MECHANICAL  DRAWING 

FOR 

SECONDARY  SCHOOLS 


BY 

FRED  D.  CRAWSHAW,  B.S.,  M.E. 

PROFESSOR  OF    MANUAL   ARTS,    THE  UNIVERSITY  OF  WISCONSIN 
AND 

JAMES  D.  PHILLIPS,  B.S. 

PROFESSOR  OF  DRAWING  AND  ASSISTANT  DEAN    COLLEGE  OF  ENGINEERING, 
""   THE  UNIVERSITY  OF  WISCONSIN 


SCOTT,  FORESMAN  AND  COMPANY 
CHICAGO  NEW  YORK 


COPYRIGHT  1916 

BY 
SCOTT,  FORESMAN  AND  COMPANY 


PREFACE 

Mechanical  Drawing  is  recognized  today  as  an  important  part 
of  a  secondary  education.  For  all  classes  of  pupils  it  serves 
as  an  important  means  of  developing  visualization,  strengthen- 
ing the  imagination,  and  forming  habits  of  careful  observation 
and  perception.  For  those  who  will  make  use  of  it  commercially, 
mechanical  drawing  is  the  accepted  means  of  creating  a  con- 
ventional picture  of  objects. 

This  book  analyzes  mechanical  drawing  upon  the  basis  of 
its  elements,  or  natural  divisions,  such  as  Perspective  Sketch- 
ing, Orthographic  Sketching,  Pencil  Mechanical  Drawing,  Ink- 
ing, Tracing,  and  Reproducing.  Each  one  of  these  divisions  is 
treated  separately  in  a  chapter.  Each  chapter  organizes  the 
division  of  drawing  which  it  represents.  Hence  in  each  chap- 
ter there  is  presented  a  progressive  series  of  problems  in  one 
of  the  natural  divisions  of  the  subject. 

The  book  contains  six  chapters  and  covers  the  first  two  years 
of  mechanical  drawing  in  Secondary  Schools.  The  first  four 
chapters  are  designed  to  occupy  the  time  of  a  class  for  the 
first  year  of  the  two  years'  course.  As  there  is  a  large  element 
of  flexibility  in  the  selection  of  problems,  no  one  individ- 
ual is  expected  to  solve  all  problems.  The  course  may  be  easily 
extended  over  a  period  of  more  than  two  years,  even  to  three 
or  four  years,  depending  upon  the  number  of  problems  solved, 
whether  a  part  or  all  of  the  chapters  are  included  in  the  course, 
and  the  time  devoted  to  the  subject  during  each  year. 

The  chapters  are  arranged  in  the  order  in  which  the  divisions 
of  drawing  are  dealt  with  in  commercial  drawing  room  practice. 
Problems,  arranged  in  groups  in  each  chapter,  progress  in  the 
order  of  their  difficulty.  Each  group  of  problems  is  chosen  to 

3 

436277 


•1  MECHANICAL.  DRAWING 

emphasize  the  construction  of  a  certain  type  of  line,  the  use 
of  particular  instruments,  and  the  application  of  commonly  used 
conventions.  It  is  believed  that  such  a  treatment  both  retains 
and  extends  all  possible  educational  values  attributed  to  mechan- 
ical drawing. 

In  those  branches  of  vocational  education  which  deal  with 
industry,  mechanical  drawing  is  the  means  of  showing  the  plan 
of  construction  or  the  method  of  assembling  constructed  parts. 
Therefore  the  authors  of  this  book  have  taken  the  view  that  all 
problems  presented  must  represent  commercial  industrial  prac- 
tice. They  have  selected  problems  which  represent  several  com- 
mon industrial  materials,  and  the  solutions  required  represent 
the  best  commercial  drawing  room  practice.  Consequently  all 
abstract  problems  have  been  eliminated  except  in  so  far  as  they 
relate  directly  to  practical  problems.  This  feature,  when  coupled 
with  the  one  of  dwelling  upon  one  division  of  drawing  until  a 
complete  series  of  problems  in  it  has  been  solved,  makes  the 
book  unique  in  its  presentation  of  unit  courses.  All  of  these 
units,  when  taken  together,  complete  the  field  of  mechanical 
drawing,  and  each  one  prepares  the  student  for  efficient  serv- 
ice in  a  particular  division  of  the  whole  field  of  drawing. 

The  course  presented  in  this  book  has  the  following  subject 
matter  features: 

1.  Every    problem    represents    typical    industrial    material, 
commercial  construction,  and  the  best  drawing  room  practice. 

2.  Every  chapter  presents  a  complete  course  in  one  of  the 
natural  divisions  of  drawing. 

3.  All  problems   are   arranged   in  groups   depending  upon 
the  elements  in  drawing  which  are  involved.     The  student  may 
select  or  the  instructor  may  assign  any  one  or  more  of  several 
problems  in  each  group,  depending  upon  student  ability   and 
community  interest.     This  feature  of  flexibility  makes  it  easy 
to  adapt  the  course  at  any  time  to  any  student  in  a  class  and 
to  any  class  in  a  community  by  any  one  or  all  of  three  means : 

(a)  A  selection  of  problems  within  a  group. 

(b)  The  addition  of  problems  to  any  group. 

(c)  The  elimination  of  any  section  of  subject  matter  or  of 
any  group  of  problems  within  a  section. 


PREFACE  5 

4.  All  chapters,  when  completed  in  the  order  in  which  they 
are  arranged,  furnish  a  complete  course,  both  in  the  subject 
of  mechanical  drawing  and  in  the  field  of  industry  covered  in 
secondary  education,  in  which  mechanical  drawing  plays  a  part. 

The  course  presented  in  this  book  has  the  following  method 
features : 

1.  A  type  problem  showing  typical  conventions  and  solu- 
tions is  furnished  for  each  group  of  problems. 

2.  Numerous  dal;a  problems,  given  in  the  form  of  freehand 
sketches  and  finished  mechanical  drawings,  present  a  standard 
in  technique. 

3.  Each  division  in  mechanical  drawing  is  analyzed  into 
its  several  elements  which   are   presented  in  a  series  of  well 
graded,  practical  problems,  involving  essential  theory  and  its 
application. 

4  Each  division  in  drawing  requires  the  concentration  of 
the  student  upon  one  thing  at  a  time  until  he  has  a  fair  mastery 
of  both  theory  and  practice.  The  next  division  reviews  this 
theory  and  practice  in  related  problems. 

5.  Each  group  of  problems  in  each  division  in  drawing  is 
accompanied  by  explicit  instruction  and  illuminating  reading 
for  the  student,  and  suggestive  demonstration  material  for  the 
instructor. 

6.  Each  chapter  in  the  first  year's  course  closes  with  a  series 
of  review  problems  and  review  questions. 

In  order  to  cover  fully  the  field  of  mechanical  drawing  for 
secondary  schools  and  to  prepare  students  for  commercial  draw- 
ing room  practice  in  the  several  divisions  of  the  subject,  the 
authors  have  given  special  attention  in  the  second  year  of  the 
two-year  course  to  such  subjects  as  Sheet  Metal  Drawing,  Archi- 
tectural Drawing,  and  Machine  Drawing.  The  student  who  com- 
pletes the  work  as  outlined  for  the  first  year  will  therefore  be 
able  to  devote  his  attention  to  any  one  of  these  subjects  or  to  all 
of  them  depending  upon  his  needs.  This  element  of  latitude  of 
choice  of  subject  matter  makes  the  book  particularly  valuable 
in  schools  where  drafting  is  taught  for  early  vocational  use. 

A  Teacher's  Manual  and  an  Outline  of  the  Course  of 
Study  are  furnished  free  to  teachers  using  the  text.  The  Manual 


6  PREFACE 

gives  brief  but  pertinent  suggestions  to  assist  the  instructor. 
The  Outline  of  the  Course  of  Study  shows  clearly  the  plan  of 
the  text  and  indicates  possibilities  of  modifying  it  to  meet  local 
conditions. 

The  authors  wish  to  express  their  appreciation  of  the  co- 
operation of  H.  D.  Orth,  Assistant  Professor  of  Drawing  and 
Descriptive  Geometry,  the  University  of  Wisconsin.  From  the 
very  beginning  to  the  end  of  the  book,  he  has  been  a  co-author 
in  its  production. 

THE   AUTHORS. 


TABLE  OF  CONTENTS 


CHAPTER  ONE 

PAGE 

PERSPECTIVE  SKETCHING   9 


CHAPTER  TWO 
ORTHOGRAPHIC  SKETCHING 66 

CHAPTER  THREE 
PENCIL  MECHANICAL  DRAWING 110 

CHAPTER  FOUR 
TRACING  AND  BLUEPRINTING 159 

CHAPTER  FIVE 

ADVANCED  DRAWING  .-...• 189 

a.  Sheet  Metal  Drawing  Problems. 

b.  Furniture  and  Cabinet  Drawing  Problems. 

c.  Machine  Drawing  Problems. 

d.  "Architectural  Drawing  Problems. 

CHAPTER  SIX 
ISOMETRIC  AND  CABINET  DRAWING 305 

CHAPTER  SEVEN 
GEOMETRICAL  CONSTRUCTIONS  319 


CHAPTER  I 

PERSPECTIVE  SKETCHING 
•   PROSPECTUS 

It  is  the  aim  of  this  chapter  to  develop  in  a  condensed  but 
thorough  manner  the  essential  principles  upon  which  perspective 
sketching  is  based.  Furthermore,  the  presentation  is  intended  to 
assist  the  student  to  develop  a  fair  degree  of  skill  in  drawing 
perspectives  of  rectangular,  angular,  and  cylindrical  objects. 
Upon  completion  of  the  work  of  this  chapter,  he  should  be  able 
to  draw  objects  composed  of  a  combination  of  these  elementary 
forms.  It  is  hoped  that  the  student  will  have  gained  confidence 
in  his  ability  to  visualize  and  represent  an  object  pictorially.  If 
this  has  been  accomplished  he  will  find  a  use  for  perspective  as 
an  interpretation  of  orthographic  drawing  which  will  be  treated 
in  the  succeeding  chapters. 


FIG.  1.     SHADED  PERSPECTIVE  OF  TRY-SQUARE 


GENERAL  PRINCIPLES 

A  perspective  drawing  of  gfn  object  shows  it  as  it  appears 
when  viewed  from  a  given  position.  Fig.  1  is  an  example  of  a 
perspective  drawing.  This  drawing  gives  the  observer  a  correct 
idea  of  the  form  and  proportion  of  the  object. 


10 


MECHANICAL  DRAWING 


The  shading  of  the  drawing,  Fig.  1,  while  adding  somewhat 
to  its  appearance,  does  not  aid  greatly  in  giving  the  correct 
impression  of  the  form  and  proportion  of  the  object.  The  shad- 
ing may,  therefore,  be  omitted,  leaving  the  simplest  kind  of 
drawing — the  outline  drawing  as  shown  in  Fig.  2.  Such  draw- 
ings will  be  referred  to  in  this  course  as  perspective  sketches. 

Perspective  sketches  are  valuable  as  a  means  of  conveying 
information  about  the  forms  of  objects  to  those  who  are  not 
familiar  with  the  more  conventional  means  of  representation 
used  in  mechanical  drawing.  The  student  will .  find  the  per- 
spective sketch  an  aid  in  interpreting  mechanical  drawing. 


FIG.  2.    PERSPECTIVE  OF  TRY-SQUARE 


In  this  course  all  objects  to  be  drawn  in  perspective  will  be 
represented  as  resting  on  a  horizontal  plane  directly  in  front  of 
the  observer  and  below  the  level  of  the  eye.  The  try-square  is 
shown  in  Fig.  2  as  an  observer  would  see  it  when  standing 
directly  in  front  of  A  B  with  his  eye  on  the  same  level  as  S. 

In  Fig.  2  the  line  marked  horizon  represents  a  line  in  space 
at  an  infinite  distance  in  front  of  the  observer.  The  eye  of  the 
observer  is  on  a  level  with  this  line  and  is,  consequently,  above 
the  level  of  the  try-square,  which  rests  on  a  horizontal  plane. 

The  horizon  or  horizon  line  is  therefore  an  imaginary  horizon- 
tal line  on  a  level  with  the  eye  of  the  observer  and  at  an  infinite 
distance  in  front  of  him.  The"  apparent  meeting  of  sky  and 
water  when  one  looks  over  a  large  body  of  water  is  an  example  of 
a  horizon.  Since  the  horizon  is  always  on  a  level  with  the  eye 
of  the  observer,  it  follows  that,  as  the  eye  is  raised  or  lowered  to 


PERSPECTIVE  SKETCHING  11 

secure  a  different  view  of  the  object,  the  horizon  will  be  raised 
or  lowered  the  same  distance. 

Direction  of  Lines  in  Perspective.  Referring  again  to  Fig.  2, 
we  note  that : 

1.  In  a  perspective  drawing  all  of  the  vertical  edges  of  the 
object   are   represented   by   vertical   lines   in   the   perspective. 
Example :  Lines  A  B  and  C  D. 

2.  In  a  perspective  drawing  all  of  the  horizontal  edges  of  the 
object  which  are  at  right  angles  with  the  direction  of  sight  of  the 
observer  are  represented  by  horizontal  lines  in  the  perspective. 
Example:  While  not  an  edge  of  the  object,  the  horizon  line, 
Fig.  2,  is  an  example  of  this  case. 

3.  In  a  perspective  drawing  all  of  the  horizontal  edges  which 
are  parallel  to  each  other,  but  not  at  right  angles  to  the  direction 
of  sight  of  the  observer,  are  represented  by  lines  which  converge 
to  a  point  on  the  horizon.    Example :  Lines  A  C  and  B  D. 

4.  Horizontal  lines  receding  to  right  and  left  in  a  perspective, 
which  make  equal  angles  with  the  horizon  line,  meet  the  horizon 
line  at  points  equally  distant  from  the  point  on  the  line  directly 
in  front  of  the  observer.     Example :  In  Fig.  2,  S  is  a  point  on 
the  horizon  line  directly  in  front  of  the  observer.    The  distance 
from  S  to  VR  is  equal  to  the  distance  from  S  to  VL. 

4o°  Perspective.  The  angle  between  the  beam  and  blade  of 
the  try-square  is  90°.  The  try-square  is  so  placed  that  the  angles 
which  the  receding  edges  to  the  right  and  to  the  left  make  with 
the  horizon  are  equal  and  must  therefore  be  45°  angles.  Because 
of  this  fact  the  try-square  is  said  to  be  drawn  in  45°  perspective. 

All  of  the  rectangular  objects  drawn  in  this  course  will  be 
placed  in  a  similar  position  to  that  of  the  try-square,  i.e.,  in  45° 
perspective.  This  will  insure  comparative  ease  in  the  construc- 
tion of  perspective  sketches,  as  will  appear  later. 

The  points  VL  and  VR  on  the  horizon  toward  which  the  hori- 
zontal receding  edges  of  the  try-square  converge  are  called 
vanishing  points. 

A  vanishing  point  is  the  common  intersection  of  two  or  more 
converging  lines  which  represent  parallel  receding  edges  of  an 
object. 

All  parallel  horizontal  receding  lines  must  converge  to  the 


12  MECHANICAL  DRAWING 

same  paint  on  the  horizon.  Example :  The  horizontal  lines  of 
the  try-square  converging  to  the  right  in  its  perspective  meet  in 
VR.  Likewise  all  the  horizontal  lines  converging  to  the  left  meet 
in  VL. 


Vertical  Lengths  in  Perspective. 

1.  Eqnal  distances  on  the  same  vertical  edge  of  an  object  are 
represented  by  equal  lengths  in  perspective.    Example :    In  Fig. 
2  the  try-square  blade  is  represented  as  entering  the  beam  mid- 
way between  the  upper  and  lower  surfaces.    The  distance  from 
A  to  the  blade  is  equal  to  the  distance  from  B  to  the  blade. 

2.  Equal  distances  on  vertical  edges  of  an  object  which  are  at 
unequal  distances  from  the  observer  are  represented  by  unequal 
lengths  in  perspective.    Example :  A  B  and  C  D  represent  equal 
lengths  on  the  object  but  are  unequal  in  the  perspective. 

3.  Of  two  equal  vertical  distances  on  an  object  the  one  nearest 
the  observer  is  represented  by  the  greater  length  in  perspective. 
Example :  A  B  and  C  D  which  represent  equal  vertical  lengths 
on  the  object  are  both  included  between  two  lines  of  the  drawing 
which  converge  toward  VR.    On  account  of  the  convergence  of  the 
two  receding  lines  C  D  is  shorter  than  A  B. 

Horizontal  Lengths  in  Perspective. 

1.  Equal  distances  on  a  horizontal  receding  edge  of  an  object 
are  represented  by  unequal  lengths  in  perspective.     Example : 
The  spaces  between  the  lines  representing  the  one-inch  marks  on 
the  try-square  blade,  Fig.  2,  are  unequal. 

2.  Of  the  equal  distances  on  a  horizontal  receding  edge  of  an 
object,  those   farthest  from  the   observer  are  represented   by 
shorter  lengths.    Example :  In  Fig.  2  the  spaces  between  the  lines 
representing  the  one-inch  marks  grow  shorter  as  they  are  farther 
away  from  the  observer. 

3  Equal  distances  on  a  horizontal  receding  edge  of  an  object 
are  represented  by  lengths  which  appear  equal.  Example  :  The 
spaces  between  the  lines  representing  the  one-inch  marks  on  the 
try-square  blade,  Fig.  2,  are  made  to  appear  equal. 


PERSPECTIVE  SKETCHING  13 

The  varying  of  the  lengths  of  lines  representing  equal 
distances  on  the  object  as  described  above  is  known  as  fore- 
shortening. 

Foreshortening  is  the  process  of  shortening  parts  of  a  perspec- 
tive of  an  object  so  as  to  give  the  impression  of  true  form  and 
proportion. 

The  Cube  in  Perspective.  Thus  far  only  a  general  considera- 
tion of  perspective  has  been  given.  The  following  is  an  applica- 
tion of  the  principles  thus  far  developed  to  the  representation  of 
a  one-inch  cube. 

In  this  course  the  cube  will  be  regarded  as  the  "basic  form  for 
all  perspective  drawing.  The  one-inch  cube  will  be  used  as  the 
unit  of  measure  and  therefore  it  is  essential  that  its  proportions 
and  position  with  reference  to  the  eye  be  well  in  mind.  In  Fig.  3 
the  eye  of  the  observer  is  directly  in  front  of  the  point  S.  The 
vertical  faces  of  the  cube  make  45°  with  the  horizon  and,  also, 
with  the  direction  in  which  the  observer  is  looking.  This  agrees 
with  the  position  of  the  try-square  in  Fig.  2  and  is  said  to  be  in 
45°  perspective  as  defined  on  page  11.  In  45°  perspective  the 
distances  from  the  point  on  the  horizon  directly  above  the  nearest 
point  of  the  object  to  the  vanishing  points  and  to  the  eye  must 
be  equal.  In  this  course  the  vanishing  points  are  taken  14"  to 
the  right  and  left  of  the  point  above  the  nearest  corner  of  the 
object. 

The  edges  of  the  cube  are  one  inch  long.  The  front  vertical 
edge  of  the  cube  will  be  the  longest  line  in  the  perspective  of  the 
cube  (See  3  under  Vertical  Lengths  in  Perspective).  It  will  be 
drawn  in  its  true  length,  one  inch. 

The  principles  already  developed  are  applied  in  the  follow- 
ing analysis  of  the  perspective  of  the  cube. 

Since  the  side  faces  are  equally  inclined  to  the  direction  in 
which  the  observer  is  looking : 

1.  Angle  D  A  E- angle  D'A  E' 

2.  Angle  F  B  H- angle  F'B  H'. 

Such  angles  will  hereafter  be  referred  to  as  the  angles  of 
inclination. 


14 


MECHANICAL  DRAWING 


The  perspective  of  the  corner  G  is  directly  above  A. 

Due  to  the  convergence  of  A  D  with  B  F  and  A  D'  with  B  F' : 

Angles  F  B  H  and  F'B  H'  are  greater  than  angles  DAE 
and  D'A  E'. 


TOVL 


OVR 


FIG.  3.    PERSPECTIVE  OF  ONE- INCH  CUBE 

Lines  D  F  and  D'F'  are  shorter  than  A  B.    D  F  =  D'F'.    Due 
to  the  convergence  of  A  D  with  D'G  and  A  D'  with  D  G : 

1.  G  D  and  G  D'  are  shorter  than  A  D  and  A  D' ; 

2.  G  C  is  shorter  than  C  A. 


Due  to  foreshortening: 

A  D  and  A  D'  are  shorter  than  A  B. 


PERSPECTIVE  SKETCHING 


15 


RECTANGULAR  OBJECTS 
PREPARATORY  INSTRUCTION  FOR  DRAV7ING  PLATE  1 

The  following  is  a  list  of  the  materials  needed  to  make  the 
perspective  sketches : 

1.  Drawing  board. 

2.  High-grade    drawing    paper    similar    to    Universal — 

9"xl2"  sheets. 

iSH 


3.  High-grade  pencils 


5H 


4.  Pencil  pointer. 

5.  Erasers — Ruby  and  Flexible  gray. 

6.  Thumb  tacks. 

7.  A  straightedge — ruler  or  triangle. 


BORDER  LINE 


FIG.  4.     POSITION  OF  SHEET  ON  DRAWING  BOARD 
\ 

The  drawing  board  should  be  made  of  well-seasoned,  straight- 
grained,  soft  wood,  free  from  knots  and  cracks. 

When  in  use  the  drawing  board  should  be  placed  on  the  desk 
with  the  longer  edges  parallel  to  the  front  edge  of  the  drawing 
table.  It  may  be  tilted  to  any  convenient  angle. 

Drawing  Paper.  In  selecting  a  drawing  paper  the  draftsman 
should  have  in  mind  the  purpose  for  which  it  is  to  be  used.  For 


16 


MECHANICAL  DRAWING 


freehand  drawing,  where  it  is  desired  to  produce  a  porous,  uni- 
form line  with  a  soft  pencil,  a  slightly  grained  surface  is  satis- 
factory. It  should  stand  erasing  without  injury. 

In  preparing  to  make  a  drawing,  a  sheet  of  paper  should  be 
tacked  near  the  upper  left  hand  corner  of  the  board  with  the 
longer  edges  parallel  to  the  longer  edges  of  the  board.  Fig.  4. 
To  fasten  the  sheet  insert  a  tack  in  the  upper  left  hand  corner ; 


T 


CORRECT  AVOID 

FIG.  5.    POSITION  OF  THUMB  TACKS 

square  the  paper  with  the  board,  and,  stretching  it  diagonally, 
insert  a  tack  in  the  lower  right  hand  corner.  Insert  a  tack  in  the 
upper  right  hand  corner,  stretch  the  sheet  in  the  direction  of  the 
lower  left  hand  corner,  and  insert  a  fourth  tack.  Press  each  tack 
down  vertically  until  the  head  is  firmly  in  contact  with  the  paper. 
Fig.  5. 

Pencils.  The  lead  of  the  drawing  pencil  should  be  of  firm, 
even  grain.  To  secure  the  desired  effect  in  the  drawing,  the 
hardness  of  the  pencil  must  be  considered  in  connection  with  the 
surface  of  the  paper.  For  freehand  drawing  a  medium  soft 
pencil  should  be  used  on  a  slightly  grained  surface.  A  soft  pencil 


PERSPECTIVE  SKETCHING 


17 


is  more  easily  controlled,  and  consequently  there  is  more  freedom 
in  drawing  lines  with  it  than  can  be  secured  with  a  hard  pencil. 
To  sharpen  the  pencil,  grasp  it  in  the  left  hand  as  illustrated 
in  Fig.  6,  and  with  the  knife  in  the  right  hand,  cut  the  shavings 
by  drawing  the  knife  toward  the  body  and  through  the  wood 


FIG  6.    SHARPENING  THE  PENCIL.    WHITTLING  AWAY  THE  WOOD 


FIG  7.    SHARPENING  THE  PENCIL.    POINTING  THE  LEAD 


only.  About  one-quarter  inch  of  lead  should  be  exposed,  and  the 
wood  tapered  back  about  one  inch  from  the  lead.  Sharpen  the 
lead  on  the  surface  of  a  sandpaper  pad  or  file,  rotating  the  pencil 
so  as  to  produce  a  conical  point.  Fig.  7.  The  sharpened  lead 
should  be  slightly  rounded  on  the  end  in  order  that  soft  lines  as 
shown  in  Fig.  8  may  be  produced.  This  figure  also  shows  the 
sketching  pencil  properly  sharpened. 


18 


MECHANICAL  DRAWING 


The  Constructive  Stage.  In  making  a  freehand  sketch  all  of 
the  straight  lines  will  first  be  drawn  very  lightly  with  the  aid  of 
a  straightedge  such  as  the  edge  of  a  triangle  or  ruler,  using 
the  5H  pencil.  Fig.  12. 

1.  When  two  points  on  a  line  are  known  the  edge  of  the  tri- 
angle or  ruler  should  be  placed  so  that  its  edge  passes  through 
both  points.     The  line  may  then  be  ruled  lightly. 

2.  Sometimes  only  one  point  on  the  line  and  its  general  direc- 
tion will  be  known.    In  this  case  the  edge  of  the  rule  should  be 
made  to  pass  through  the  point  with  the  edge  adjusted  to  the 
proper  direction. 


FINISHING    LINt 


4 
NCH 


MEDIUM     PENCIL 


CONSTRUCTION    LINE 

HARD    PENCIL 

FIG.  8.     SKETCHING  PENCIL  PROPERLY   SHARPENED 


Ruling  a  Line.  In  ruling  a  line  along  a  straightedge  the 
pencil  is  held  in  the  hand  as  indicated  in  Fig.  13.  The  line  is 
drawn  with  a  continuous  motion  from  left  to  right  with  the  tip 
of  the  fourth  finger  touching  the  ruler  to  steady  the  hand.  The 
forearm  should  always  be  at  right  angles  with  the  line  being 
drawn.  The  rule  should  preferably  be  between  the  draftsman 
and  the  line  being  drawn. 

The  Finishing  Stage.  When  the  constructive  stage  has  been 
completed  all  lines  which  will  not  appear  in  the  finished  drawing 
should  be  erased.  The  3H  pencil  should  then  be  properly  sharp- 
ened and  the  lines  of  the  drawing  traced  over  freehand.  They 
must  be  uniform  in  width  and  grayness  of  tone. 

The  Position  of  the  Hand  and  Pencil  in  Sketching.  In  draw- 
ing a  freehand  line  the  pencil  is  held  firmly,  but  not  rigidly, 
between  the  first  two  fingers  and  the  thumb  as  in  writing. 

In  sketching  a  horizontal  line  the  ends  of  the  third  and  fourth 
fingers  should  rest  upon  the  board  to  help  support  and  steady 


PERSPECTIVE  SKETCHING 


19 


the  hand.     Fig.  9.     With  the  forearm  resting  on  the  drawing 
board,  the  hand  should  be  moved  from  left  to  right,  hinging  at 


FIG.  9.     SKETCHING  A  HORIZONTAL  LINE 

me  wrist.  This  will  permit  only  short  strokes,  about  one  inch 
long,  to  be  taken.  To  sketch  a  long  line,  therefore,  one  must 
join  together  a  series  of  one-inch  lines.  The  position  for  each 


FIG.  10.     SKETCHING  A  VERTICAL  LINE 

stroke  should  be  obtained  by  moving  the  hand  and  forearm  in  the 
direction  of  the  line.  Each  section  should  be  joined  to  the  pre- 
ceding one,  but  not  lapped  upon  it,  as  the  lapping  of  sections 
produces  an  undesirable  sketchy  effect. 


20  MECHANICAL  DRAWING 

In  sketching  a  vertical  line  the  hand  is  placed  in  the  position 
shown  in  Fig.  10.  The  hand  rests  upon  its  side  instead  of  upon 
the  ends  of  the  third  and  fourth  fingers.  The  pencil  is  moved 
downward.  The  strokes  are  made  with  a  finger  movement  while 
the  hand  remains  stationary.  In  sketching  a  vertical  line  the 
forearm  should  remain  approximately  in  the  position  of  a  vertical 
line  on  the  sheet. 

The  Border  Rectangle.  Before  starting  the  drawing  of  the 
object  on  the  sheet,  draw  a  border  line  approximately  one-half 
inch  from  each  edge  of  the  sheet.  This  may  be  done  in  the  con- 
structive stage  by  placing  the  straightedge  parallel  to  each  edge 
of  the  sheet  at  a  distance  estimated  to  be  one-half  inch  in  from 
the  edge,  and  ruling  a  line  lightly.  This  border  rectangle  should 
be  traced  over  freehand  in  the  finishing  stage  as  are  the  lines  of 
the  sketch. 

DATA  FOE  DRAWING  PLATE  1 

Given:     The  perspective  of  a  cube,  Fig.  11. 
Required:     To  make  a  perspective  sketch  similar  to  that 
shown  in  Fig.  11,  on  a  9"  x  12"  sheet  as  explained  below. 

Instructions: 

1.  Draw  lightly  the  border  rectangle  J"  from  the  edge  of 
the  sheet. 

2.  To  locate  the  perspective  of  the  cube  use  the  5H  pencil  with 
the  ruler  as  a  straightedge. 

a.  Draw  two  very  light  horizontal  lines  XVR  and  YZ 

dividing  the  space  between  the  upper  and  lower  bor- 
der lines  into  three  equal  parts. 

b.  Draw  a  vertical  line,  VW,  through  the  center  of  the 

sheet  and  SIT  midway  between  VW  and  the  left 
border  line. 

c.  From  B  estimate  one  inch  up  on  S  U,  thus  locating  A, 

the  upper  front  corner  of  the  cube. 

3.  VR  is  about  J"  from  the  right  border  line. 

4.  Draw  lightly  a  horizontal  line  through  A  and  connect  A 
with  VR. 


PERSPECTIVE  SKETCHING 


21 


5.  Get  the  direction  of  A  D'  by  drawing  the  angle  of  inclina- 
tion D'A E'  equal  to  angle  DAE.    This  may  be  accomplished  by 
placing  the  ruler  so  that  the  edge  passes  through  point  A  and 
adjusting  its  direction  until  the  angles  appear  equal.     Fig.  12. 

6.  To  obtain  the  width  of  a  vertical  face  of  the  cube,  draw 
DF  so  that  the  figure  ADFB  appears  as  a  square.     Fig.  13 
shows  the  process  of  locating  D  F.  A  ruler  or  triangle  is  placed 


FIG  11.    PERSPECTIVE  OF  CUBE 

with  an  edge  in  a  vertical  position  parallel  to  the  line  A  B.  It  is 
then  moved  back  and  forth  to  right  and  left  until,  in  the  judg- 
ment of  the  draftsman,  the  figure  ADFB  appears  as  a  square. 

7.  Draw  D'F'  making  AE'=AE.    Complete  the  perspective 
of  the  cube  by  drawing  D'VR  and  D  G.    Fig.  11. 

This  completes  the  constructive  stage. 

8.  All  lines  not  shown  in  Fig.  11  should  now  be  erased.    The 
cube  and  the  border  rectangle  should  be  traced  over  freehand 
with  a  well  sharpened  3H  pencil  to  produce  a  line  of  even  weight 
and  uniform  shade.    The  remaining  lines  of  the  drawing  should 


22 


MECHANICAL  DRAWING 


be  allowed  to  remain  light,  as  drawn  in  the  constructive  stage. 
Omit  all  reference  letters. 

9.  Write  the  plate  number  and  name  in  the  lower  right  hand 
corner  of  the  sheet  as.  in  Fig.  11.  Remove  the  sheet  from  the 
board,  turn  it  over  and,  with  a  knife  or  other  sharp  instrument, 
press  the  paper  back  into  the  thumb  tack  holes. 

The  Method  of  Developing  Lettering  in  the  Course.  One  of 
the  most  difficult  steps  in  making  a  drawing  is  the  lettering  of 
the  notes,  dimensions,  and  title.  In  this  course  lettering  will  be 
omitted  from  all  drawings  until  the  student  has  had  considerable 
practice  in  forming  and  spacing  the  letters  and  figures.  This 
practice  will  be  had  on  small  lettering  plates.  Each  drawing 
plate  should  be  followed  by  the  lettering  plate  of  the  same 
number. 


FIG.  12.    SKETCHING  THE  ANGLES  OF  INCLINATION 


LETTERING 

Modern  practice  demands  that  the  lettering  done  on  working 
drawings  be  simple,  legible,  and  capable  of  easy  and  rapid  ren- 
dition. The  simple  Gothic  style  fulfils  these  requirements  and 
is  therefore  quite  generally  used. 

Form  and  Proportion.  A  careful  study  of  the  form  and 
proportion  of  each  letter  must  be  made  before  the  student  can 
hope  to  make  any  considerable  progress  in  lettering.  Practice 


PERSPECTIVE  SKETCHING  23 

in  drawing  the  letters  will  add  something  to  his  control  of  the 
media  with  which  he  works,  but  first  of  all  he  must  have  a  dis- 
tinct knowledge  of  what  he  is  trying  to  accomplish. 

Strokes.  For  convenience  in  forming  letters  they  are  divided 
into  strokes.  In  most  cases  the  strokes  are  natural  divisions  of 
the  outline  of  the  letter.  Three  things  should  be  remembered 
about  the  strokes  for  each  letter:  (1)  the  number  of  strokes, 
(2)  the  order  in  which  they  are  made,  (3)  the  direction  in  which 
each  stroke  is  drawn.  The  advantage  in  knowing  and  using  a 
system  of  strokes  lies  in  the  fact  that  drawing  the  letters  repeat- 
edly in  the  same  manner  makes  the  forming  of  each  letter  more 


FIG.  13.     DETERMINING  THE  WIDTH  OF  THE  FACE  OF  THE  CUBE 

nearly  automatic.  Hence  it  adds  to  the  ease  with  which  letters 
can  be  produced  and  aids  in  securing  uniform  results. 

Spacing.  Second  only  in  importance  to  the  forms  of  the  let- 
ters is  their  relation  to  each  other.  The  best  effect  is  obtained 
when  the  areas  included  between  the  letters  in  a  word  appear 
equal.  For  the  capital  letters  the  area  of  these  spaces  should 
be  equal  to  the  area  of  a  rectangle  one-half  the  normal  width 
of  the  II.  The  space  between  words  should  be  about  three  times 
that  between  letters.  Words  set  off  by  a  comma  should  be  spaced 
from  one  to  one  and  one-half  times  the  usual  distance.  The  space 
between  sentences  should  be  about  twice  the  space  between  words. 

The  final  test  of  good  spacing  is  legibility.  The  letters  must 
be  far  enough  apart  to  avoid  a  crowded  effect  and  yet  the  spaces 
must  not  be  so  great  that  the  letters  armear  scattered.  In  like 


24  MECHANICAL  DRAWING 

manner  words  must  be  separated  enough  to  stand  out  individ- 
ually, but  not  enough  to  make  reading  difficult. 

Lettering  in  Pencil.  The  pencil  used  for  the  freehand  work 
on  a  drawing  should  be  softer  than  the  pencil  used  for  the 
mechanical  work.  It  should  be  of  such  grade  that  when  prop- 
erly sharpened  a  clear  gray  line  can  be  produced  with  a  single 
stroke.  It  should  not  be  hard  enough  to  cut  into  the  surface  of 


FIG.  14.    CORRECT  POSITION  OP  THE  HAND  AND  PEN  FOR  LETTERING 

the  paper,  as  difficulty  is  then  experienced  in  controlling  the 
direction  of  the  line. 

The  lead  should  be  sharpened  to  a  long  taper,  conical  in 
form  and  rather  blunt  at  the  end.  With  one-quarter  inch  of 
lead  exposed,  and  this  tapered  back  to  the  wood,  the  section 
of  the  lead  will  be  so  nearly  uniform  near  the  end  that  it  will 
stand  considerable  use  without  resharpening.  The  pencil  should 
be  held  in  the  hand  in  the  same  position  as  the  pen  shown  in 
Fig.  14,  with  the  forearm  nearly  in  the  direction  of  the  vertical 
stems  of  letters  or,  in  the  case  of  the  inclined  letters,  nearly  in 
the  direction  of  the  slant.  The  strokes  should  be  drawn  with  a 
finger  movement.  The  pencil  should  be  turned  about  its  axis 


PERSPECTIVE  SKETCHING  25 

frequently  to  keep  the  point  round  so  as  to  prodrce  a  line  of 
uniform  weight.  All  strokes  should  be  made  with  the  hand  held 
in  the  same  position  Shifting  the  arm  to  obtain  advantageous 
positions  for  drawing  strokes  in  different  directions  is  a  habit 
which  will  prevent  the  acquirement  of  commercial  speed  and  at 
the  same  time  will  prevent  the  development  of  the  professional 
type  of  lettering  as  distinct  from  the  labored  effect  produced  by 
the  average  novice. 

Lettering  in  Ink.  The  beginner  will  find  it  more  difficult  to 
produce  satisfactory  results  with  pen  and  ink  than  with  the 
pencil  because  of  the  complications  which  arise  from  the  nature 
of  the  media.  To  secure  a  black  line  of  uniform  weight  with  a 
quick  drying  fluid  such  as  India  ink,  and  with  an  ordinary 
writing  pen,  presents  a  problem  which  usually  requires  a  careful 
study  of  the  methods  of  using  these  materials  and  considerable 
intelligent  practice. 

The  pen  should  be  held  in  the  hand  as  shown  in  Fig.  14. 
In  drawing  a  line  the  points  of  the  pen  should  be  side  by  side 
so  that  the  width  of  the  line  can  be  controlled  by  the  pressure 
applied  to  spread  the  nibs.  The  position  of  the  pen  in  the  hand 
should  not  be  changed  for  strokes  of  different  direction,  but 
rather  the  weight  of  line  should  be  kept  uniform  by  varying  the 
pressure  on  the  pen.  In  lettering  in  ink  as  in  lettering  with  the 
pencil,  the  hand  should  be  held  in  the  same  position  for  all 
strokes.  This  will  give  a  better  general  effect  and  will  make  it 
easier  to  develop  commercial  speed  in  forming  the  letters. 

The  pen  should  be  filled  by  applying  the  quill  attached  to  the 
stopper  of  the  ink  bottle  to  the  under  side  of  the  pen.  Enough 
ink  should  be  put  on  the  pen  to  last  a  reasonable  length  of  time 
and  to  produce  a  wet  line  so  that  when  it  is  dry,  enough  carbon 
will  have  been  deposited  to  make  it  black.  Overloading  the  pen, 
on  the  other  hand,  will  cause  the  corners  to  fill  at  intersecting 
lines.  The  pen  should  be  wiped  frequently  to  remove  the  dry 
ink  from  the  surfaces  of  the  pen  and  between  the  nibs.  Fresh 
ink  and  a  clean  pen  are  necessary  to  produce  sharp  clean-cut 
lines. 

Titles.  The  title  contains  information  by  which  the  drawing 
can  be  identified,  such  as  the  name  of  the  part  or  parts  of  the 


26 


MECHANICAL  DRAWING 


machine  or  structure,  name  of  the  complete  machine  or  structure, 
manufacturer's  firm  name  and  address,  drawing  number,  date, 
scale,  and  initials  of  draftsman,  tracer,  and  checker. 

The  usual  position  of  the  title  is  in  the  lower  right-hand 
corner  of  the  sheet  where  it  does  not  interfere  with  the  drawing 
and  at  the  same  time  may  be  read  without  taking  the  sheet  from 
its  place  in  a  drawer  or  file.  The  relative  importance  of  the 
items  in  the  title  is  shown  by  varying  heights  and  widths  of  the 
letters  or  the  weight  of  their  stems,  or  both. 

The  lines  should  be  balanced,  i.e.,  the  middle  point  of  each 
line  should  fall  on  the  same  vertical  line.  To  give  the  best  effect 


Ntoli/  fionovi 


FIG.  15.     TITLE  MATERIAL  DIVIDED  INTO  GROUPS  OF  WORDS 


the  lines  should  vary  in  length.  The  general  contour  of  the  title 
is  very  commonly  oval  or  pyramidal  in  form. 

The  arrangement  of  the  lines  of  the  title  and  the  determina- 
tion of  the  height  of  each  line  present  a  problem  in  design  for 
the  solution  of  which  the  contour  of  the  title  should  be  kept  in 
mind. 

The  space  between  the  lines  of  letters  for  the  single  stroke 
capitals  should  be  from  three-fourths  to  one  and  three-fourths 
the  height  of  the  smallest  adjacent  letters. 

The  style  of  letter  used  for  the  tit/e  -should  be  dignified.  For 
this  reason  the  capital  letters  are  generally  used. 

The  steps  in  designing  a  title  should  be  taken  in  about  the 
following  order: 

1.  Assuming  that  the  wording  or  at  least  the  substance  of 
the  title  is  stated,  write  ont  the  complete  title  and  divide  the 
words  into  logical  grouDs  for  the  differpjeit  lines.  Fig.  15. 


PERSPECTIVE  SKETCHING  27 

2.  Rewrite,  tentatively  arranging  the  lines  as  they  will  be 
in  the  printed  title.    Fig.  16. 

3.  Decide  upon  the  relative  importance  of  the  lines  and  select 
heights  of  letters  accordingly.     It  may  now  appear  that  a  re- 
arrangement of  the  lines  will  give  a  better  outline  without  affect- 
ing the  meaning. 


i"* 

V  fyowlg 

TlwiMA^^  i" 

FIG.  16.     TENTATIVE  ARRANGEMENT  OF  LINES  OF  THE  TITLE 

4.  The  title  may  be  balanced  by  printing  each  line  lightly  in 
its  proper  space  to  obtain  the  spacing  of  the  letters.  Any 
adjustment  necessary  to  make  the  middle  point  of  each  line  fall 
on  the  center  line  of  the  title  should  be  made.  The  letters  should 
then  be  drawn  in  full  weight.  This  method  may  be  used  with 

ANNUAL   EXHIBIT 

WEST  DIVISION   HIGH  SCHOOL 
DEPARTMENT  OF  MANUAL  ARTS 

MILWAUKEE  WISCONSIN 

FIG.  17.    FINISHED  TITLE 

success  by  those  who  have  had  considerable  experience  in  letter- 
ing. The  beginner  will  obtain  better  results  with  but  little  more 
work  by  lettering  the  lines  first  on  a  trial  sheet  to  get  the  spacing 
and  then  by  using  these  lines  as  a  guide  in  balancing  the  lines 
and  spacing  the  letters  on  the  drawing,  as  described  on  page  140. 
Fig.  17  shows  a  balanced  title. 

In  drafting  offices  or  business  firms  where  large  numbers  of 
drawings  similar  in  general  character  are  made,  the  items  com- 


28 


MECHANICAL  DRAWING 


mon  to  all  titles  are  very  often  printed  on  the  pencil  drawing 
with  a  rubber  stamp  and  on  the  tracing  in  type.  Uniformity  in 
treatment  is  thus  secured  and  much'  time  in  lettering  is  saved. 
Fig.  144  illustrates  commercial  titles.  These  title  forms  are 
printed  on  the  under  side  of  the  tracing  cloth.  Errors  may  thus 
be  corrected  and  changes  made  in  the  lettering  done  by  the 
draftsman  without  erasing  the  printed  lines  and  letters. 


EDGE  OF  CARD^        =  | 


BORDER 


'-f 


5" 


FIG.  18.    LETTERING  CARD 

PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  1 

The  Plate.  The  first  ten  lettering  plates  will  be  in  pencil. 
Three  by  five  cards  of  the  regular  drawing  paper,  ruled  as  shown 
in  Fig.  18,  will  be  used. 

The  Lettering  Pencil.  Use  the  3H  pencil  for  lettering,  sharp- 
ened to  a  conical  point  as  for  freehand  sketching.  Fig.  8. 

Number,  Order,  and  Direction  of  Strokes.  Each  letter  or 
numeral  is  made  by  one  or  more  strokes.  In  general,  vertical 
and  inclined  strokes  are  made  downward  and  horizontal  strokes 


PERSPECTIVE  SKETCHING 


29 


to  the  right.  Fig.  19  shows  the  number,  order,  and  direction 
of  strokes  for  the  numerals  1,  4,  7,  and  the  symbols  used  for 
the  foot,  inch,  and  dash.  The  relative  width  of  numerals  is 
shown  in  column  4. 


STROKES 


__.,,! 


WIDTH 


4-7" 


FIG.  19.    ORDER,  NUMBER,  AND  DIRECTION  OF  STROKES 

The  Scale  of  Heights.  For  convenience  in  estimating  ver- 
tical distances  the  space  between  the  guide  lines  is  divided  into 
four  equal  parts.  Fig.  19. 

A  Scale  of  Widths.  The  width  of  the  H  is  taken  as  the  unit 
of  width.  The  total  letter  distance  is  divided  into  four  equal 
parts.  Horizontal  distances  may  be  estimated  by  observing 
their  relation  to  these  divisions.  Fie.  19. 


30  MECHANICAL  DRAWING 

Drawing  the  Strokes.  Before  starting  a  stroke,  carefully 
plan  its  position  and  direction.  Make  each  line  with  one  move- 
ment of  the  pencil.  A  vertical  stroke  is  made  by  drawing  a 
line  from  one  point  to  another  directly  beloiv  it.  In  case  a  stroke 
or  letter  is  unsatisfactory  it  should  be  erased  and  redrawn. 

Foot  and  Inch  Marks.  A  short  dash  placed  to  the  upper 
right  of  a  numeral  indicates  feet.  Two  such  dashes  similarly 
placed  indicate  inches.  A  horizontal  dash  is  placed  between 
numerals  representing  feet  and  inches.  See  Fig.  19. 


3  1. 

1 

i/ 

II     II! 

1   1 

1 

1   1   1 

1 

^ 

INN 

111  = 

z4 

4 

444 

4 

4 

44 

4 

141 

144  z 

=7 

7 

777 

7 

7 

7  7 

7 

147 

I747f 

~T 

7' 

7'       4   4 

4 

4 

47' 

4" 

7"     74" 

17"     41'Z 

~7'- 

4" 

47-7" 

174-4" 

471-7" 

714-7" 

44-l"Z  ' 

FIG.  20.     LETTERING  PLATE  1.     1;  4,  7 
DATA  FOR  LETTEKING  PLATE   1 

Given:     Plate  1  to  reduced  size,  Fig.  20. 
Bequired:     To  make  the  plate  to  an  enlarged  scale. 

Instructions: 

1.  Fasten  the  card  to  the  board  either  with  thumb  tacks  or 
by  inserting  its  corners  in  diagonal  slits  cut  in  a  larger  piece 
of  paper  which  is  tacked  to  the  board.     Fig.  18. 

2.  Draw  the  numerals  and  symbols,  using  the  number,  order, 
and  direction  of  strokes  shown  in  Fig.  19. 

3.  Write  in  the  plate  number,  followed  by  the  name  at  the 
top  of  the  sheet  as  indicated  in  Fig,  20. 


PERSPECTIVE  SKETCHING  31 


PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  2 

Plate  1,  page  21,  gave  practice  in  making  a  perspective  of 
the  unit  of  measure  and  basic  form  in  perspective — the  cube. 
The  one-inch  cube  will  be  used  in  the  following  plates  as  a 
means  of  constructing  and  proportioning  the  perspective  sketches 
of  more  complex  objects. 

A  Scale  of  Levels.  Fig.  21  shows  a  horizontal  square  at  dif- 
ferent levels  in  perspective.  At  the  left  in  Fig.  22  the  horizontal 
square  is  used  as  the  top  of  a  cube,  represented  at  levels  one-half 
inch  apart.  It  will  be  noticed  that  in  each  of  these  figures  the 


FIG.  21.     VAKiAfioN  CF  AREA  WITH  LEVEL 

area  of  the  figure  representing  the  square  and  the  angle  of 
inclination  increase  with  the  distance  below  the  level  of  the  eye. 
The  distance  below  the  level  of  the  eye  of  the  front  corner  of 
each  square,  Fig.  22,  is  indicated  by  the  numerals  at  the  left  of 
the  figure.  In  this  course  the  student  will  be  aided  in  determin- 
ing the  level  for  the  perspective  of  an  object  by  referring  to  this 
scale.  To  the  right  of  the  scale  is  shown  its  application  in  repre- 
senting a  cube  at  different  levels. 

Vertical  Measurements.  Under,  "Vertical  Lengths  in  Per- 
spective/ '  page  12,  the  general  facts  regarding  these  measure- 
ments are  given.  In  making  vertical  measurements  in  per- 
spective the  following  rule  must  be  observed. 

All  vertical  distance's  on  an  object  must  be  measured  in  per- 
spective on  the  line  representing  the  front  vertical  edge  of  the 
object.  This  is  true  for  the  following  reasons : 


32 


MECHANICAL  DRAWING 


1.  The  front  vertical  edge  is  drawn  full  length.  In  Fig.  23, 
AB  is  greater  than  the  vertical  line  through  I.  To  secure  this 
length,  one  would  determine  AB  and  draw  the  vanishing  lines. 


HORIZON 


FIG.  22.    SCALE  OP  LEVELS 


2.  In  general,  equal  vertical  distances  are  equal  in  perspective 
only  when  measured   on   the   same  vertical  edge.     Example: 


PERSPECTIVE  SKETCHING 


33 


34 


MECHANICAL  DRAWING 


Horizontal  Measurements.  Under,  ''Horizontal  Lengths  in 
Perspective,"  page  12,  the  general  facts  regarding  horizontal 
measurements  are  given.  In  making  horizontal  measurements  in 
perspective  the  following  method  should  be  used : 

Whenever  possible,  horizontal  distances  on  an  object  should 
be  measured  in  perspective  by  drawing  the  faces  of  a  series  of 
receding  one-inch  cubes  so  that  they  appear  to  be  squares.  In 
Fig.  23,  lengths  A  D,  D  E,  E  G,  G  H,  and  H  1,  representing  equal 
horizontal  distances,  are  measured  by  making  faces  1,  2,  3,  4,  and 
5  appear  as  squares. 


FIG.  24.    ENCLOSING  SOLID 


The  Enclosing  Solid.  In  using  the  methods  of  making  hori- 
zontal and  vertical  measurements  given  above,  one  of  the  impor- 
tant steps  in  the  construction  of  the  perspective  sketch  will  be 
the  drawing  of  a  rectilinear  solid  the  edges  and  surfaces  of  which, 
so  far  as  possible,  are  coincident  with  the  edges  and  surfaces  of 
the  object.  Fig.  24.  This  solid  will  be  called  the  enclosing  solid. 
This  solid  should  be  drawn  completely  before  any  attempt  is 
made  to  construct  the  details  of  the  object  in  perspective. 

The  Measure  Cube.  The  first  step  in  drawing  the  enclosing 
solid  is  to  draw  a  one-inch  cube  with  its  upper  front  corner  at 
the  level  required  for  the  perspective  of  the  object  to  be  drawn. 
This  one-inch  cube  will  be  at  the  upper  front  corner  of  the  enclos- 


PERSPECTIVE  SKETCHING  85 

ing  solid.  The  front  vertical  edge  of  the  cube  serves  as  the  ver- 
tical unit  of  measure  and  the  width  of  the  side  fac^s  as  the  hori- 
zontal unit  of  measure.  This  cube  is  therefore  called  the  measure 
cube. 

The  Table  Line.  When  an  object  rests  on  a  horizontal  sur- 
face its  position  with  reference  to  that  surface  is  shown  by  a 
horizontal  line  called  the  table  line.  The  position  of  this  line  as 
shown  in  Fig.  27  is  taken  arbitrarily.  In  its  relation  to  the 
perspective  it  should  represent  the  object  as  resting  in  a  pleasing 
position  on  a  horizontal  plane.  The  table  line  should  be  drawn 
freehand. 

DATA  FOR  DRAWING  PLATE  2 

• 

Given:  The  dimensioned  perspective  of  a  sandpaper  block, 
Fig.  27. 

Required:  To  make  a  sketch  of  the  sandpaper  block,  full 
size  in  perspective,  omitting  all  dimensions  and  lettering,  or  any 
similar  problem  assigned  by  the  instructor. 

Instructions: 

1.  Draw  the  border  rectangle  as  in  Plate  1,  page  21.     Here 
and  throughout  the  constructive  stage  use  the  5H  pencil. 

2.  To  locate  the  center  of  the  sheet  proceed  as  follows :    Place 
the  ruler  on  the  sheet  with  one  edge  in  the  position  of  one  of  the 
diagonals  of  the  border  rectangle.     Rule   a   light,   short  line 
through  the  approximate  center  of  the  sheet.     In  like  manner 
draw  a  part  of  the  other  diagonal.     The  intersecting  lines  will 
locate  the  center  of  the  sheet. 

3.  With  the  aid  of  the  ruler  draw  the  measure  cube  with  its 
upper  front  corner  A  at  the  center  of  the  sheet  and  3£"  below 
the  level  of  the  eye.    Fig.  25.    Refer  to  the  angle  of  inclination 
in  Fig.  22  for  the  required  level.     Reproduce  this  angle  as 
illustrated  in  Fig.  12. 

4c  Complete  the  enclosing  solid  by  drawing  the  lines  in  the 
order  indicated  *  by  the  numerals.  Fig.  25.  Measure  vertically 
ind  to  the  right  and  left  as  previously  described  under,  "  Vertical 
Measurements ' '  and,  ' '  Horizontal  Measurements ' '  respectively, 
pages  31  and  34. 


36 


MECHANICAL  DRAWING 


5.  To  sketch  the  open  space  through  the  sandpaper  block 
which  is  to  be  occupied  when  the  block  is  in  use  by  a  block  of  the 


FIG.  25.    CONSTRUCTIVE  STAGE.    ENCLOSING  SOLID 

same  dimensions  as  the  open  space  which  holds  the  edges  of  the 
sandpaper,  locate  B,  %"  below  A,  and  draw  line  10  converging 


13 


14- 


FIG.  26.    CONSTRUCTIVE  STAGE.    COMPLETE 

with  line  3,  Fig.  26.  Lay  off  from  A  on  line  3  a  distance  repre- 
^uting1  %".  The  principle  of  foreshortening  applied  here  will 
make  this  distance  slightly  greater  than  one-half  of  the  width 


PERSPECTIVE  SKETCHING 


37 


of  the  face  of  the  cube.  Draw  line  11.  In  the  same  manner  lo- 
cate and  draw  line  12.  Draw  lines  13,  14,  and  15  converging 
with  lines  2  and  6.  Draw  line  16  vertically  from  the  intersection 
of  lines  7  and  13.  Draw  line  17  converging  with  lines  3  and  7. 
This  completes  the  constructive  stage. 

6.  Erase  all  lines  except  the  outline  of  the  figure  and  trace 
over  the  sketch  freehand  with  a  carefully  sharpened  3H  pencil. 
Draw  a  table  line  as  in  Fig.  27. 


FIG.  27.    SAND  PAPER  BLOCK 

7.  Write  the  plate  number  and  name  in  the  lower  right  hand 
corner  of  the  sheet  and  press  the  paper  back  into  the  thumb  tack 
holes  as  directed  in  Plate  1,  page  21. 

PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  2 

Curved  Strokes.  In  making  the  curved  strokes  of  the  5  and 
the  2  the  student  should  have  in  mind  the  form  of  the  complete 
oval. 

The  Dimension  Form.  The  dimension  form  consists  of  the 
numerals  designating  feet  and  inches,  the  foot  and  inch  marks, 
the  dash,  the  dimension  and  extension  lines,  and  the  arrowheads 
as  arranged  in  Fig.  77. 

It  will  be  seen  that  the  arrowheads  are  placed  on  the  dimen- 
sion lines  with  their  points  touching  the  extension  lines.  They 


38 


MECHANICAL  DRAWING 


are  composed  of  two  slightly  curved  lines  symmetrical  with 
respect  to  the  dimension  line.  The  length  of  the  arrowhead 
should  be  about  -J"  and  the  width  -f-/'.  Fig.  77.  Fig.  28  shows 
strokes  for  arrowheads  pointing  in  different  directions. 


STROKES 


WIDTH 


± 


FIG.  28.    LETTERING  PLATE 
DATA  FOR  LETTERING  PLATE  2 

Given:     Plate  2  to  reduced  size,  Fig.  29. 
Required:     To  make  the  plate, to  an  enlarged  scale. 
Instructions:    Proceed  as  in  Plate  1,  page  30,  following  care- 
fully the  number,  order,,  and  direction  of  strokes. 


PERSPECTIVE  SKETCHING 


39 


DATA  FOR  EXTRA  DRAWING  PLATE 

Given:     A  dimensioned  perspective  sketch  of  a  clamping 
plate  for  lathe  tail-stock. 


55555 
22222 


122-5"- 


\415   545   75457= 
425  5272   27527= 

TTTTTTTTTr= 


475- 2—  >\    [—- 2'- 


FIG.  29.    LETTERING  PLATE  2 


Required:     To  make  a  sketch  of  the  clamping  plate  full 
size,  omitting  all  dimensions. 


FIG.  30.     CLAMP  FOR  TAIL  STOCK 


The  upper  front  corner  of  the  enclosing  solid  is  in  the  center 
of  the  sheet  and  3J"  below  the  level  of  the  eye. 


40 


MECHANICAL  DRAWING 


ANGULAR  OBJECTS 
PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  3 

To  Center  a  Perspective  Sketch  on  a  Sheet.  For  the  pre- 
ceding plates  definite  instructions  have  been  given  to  center  the 
sketch,  on  the  sheet.  For  the  sake  of  appearance  a  sketch  should 
be  centrally  located.  The  student  should  use  considerable  care, 
therefore,  in  locating  the  upper  front  corner  of  the  enclosing 
solid.  It  cannot  always  be  located  at  the  center  of  the  sheet. 
The  following  suggestions  will  be  of  value  in  locating  the  upper 
front  corner  of  the  enclosing  solid. 

A  close  approximation  can  be  made  to  the  correct  position  of 
the  front  vertical  edge  of  the  enclosing  solid  to  right  or  left  of 
the  center  of  the  sheet  by  referring  to  Fig.  23. 


FIG.  31.    ENCLOSING  SOLID 

1.  On  this  figure  the  distance  to  be  measured  to  the  right  and 
to  the  left  of  the  front  vertical  edge  of  the  enclosing  solid  may 
be  marked  off.    If  the  horizontal  distance  ^between  the  extreme 
points  is  divided  into  two  equal  parts  the  division  will  come  at 
the  point  in  the  perspective  which  should  be  at  the  center  of  the 
sheet. 

2.  The  distance  from  A  B,  Fig.  32,  to  this  middle  point  is  the 
distance  which  the  front  vertical  edge  of  the  enclosing  solid 
must  be  to  the  right  or  left  of  the  center  of  the  sheet. 

In  locating  the  upper  front  corner  of  the  measure  cube  after 
the  position  of  the  front  edge  is  determined,  the  length  of  the 
front  edge  of  the  enclosing  solid  and  the  distance  of  the  back 
corner  of  the  upper  surface  above  the  front  corner  of  the  enclos- 


PERSPECTIVE  SKETCHING 


41 


ing  solid  must  be  estimated.    Half  the  sum  of  these  two  distances 
should  fall  above  and  half  below  the  center  of  the  sheet. 

DATA  FOR  DRAWING  PLATE  3 

Given:  The  dimensioned  perspective  sketch  of  a  cord- wind 
with  the  upper  surface  3"  below  the  level  of  the  eye.  Fig.  33. 

Required:     One  of  the  two  solutions  as  stated  below. 

1.  To  draw  the  cord-wind,  full  size,  with  the  upper  surfaces 
5"  below  the  level  of  the  eye.  Omit  all  dimensions  and  letters 
.from  the  finished  sketch. 


FIG.  32.    CONSTRUCTIVE  STAGE  COMPLETE 

2.  To  draw  the  cord-wind  full  size  with  the  upper  surface  5" 
below  the  level  of  the  eye,  and  turned  so  that  the  longer  edges 
vanish  toward  the  left  instead  of  toward  the  right. 

3.  To  draw  any  similar  object  assigned  by  the  instructor. 


FIG.  33.    CORD-WIND 

Instructions: 

1.  Locate  the  upper  front  corner  of  the  measure  cube  A  as 
directed  under,  "To  Center  a  Perspective  Sketch  on  a  Sheet," 
page  40. 


42 


MECHANICAL  DRAWING 


2.  Complete  the  enclosing  solid  as  in  Plate  2,  page  35,  taking 
care  to  secure  the  necessary  convergence.    As  it  is  the  aim  that 
the  student  should  learn  to  make  perspective  sketches  entirely 
freehand  he  should  now  draw  as  many  as  possible  of  the  lines  of 
the  constructive  stage  without  the  use  of  a  straightedge. 

3.  To  locate  the  lines  representing  the  cut  in  the  near  end 
of  the  cord-wind  lay  off  A  F  and  D  E,  Fig.  32,  to  represent  one 


FIG.  34.    LETTERING  PLATE 


inch  and  H  F  and  E  I  to  represent  one-half  inch.  From  H  and  I 
draw  lines  converging  with  A  N  and  D  M  to  the  right.  Lay  off 
A  K  to  represent  two  inches  and  draw  a  line  from  K  converging 
with  A  D.  This  line  meets  the  lines  from  H  and  I  in  L  and  TT 
respectively.  Connect  E  0  and  F  L.  From  0  draw  a  vertical 
line  and  from  P  a  line  converging  with  K  0.  These  lines  inter- 
sect in  Q.  Draw  R  Q. 

By  a  similar  method  make  the  construction  for  the  cut  at  the 
farther  end  of  the  cord  wind. 

4.  Erase  unnecessary  lines  and  finish  the  sketch  in  the  usual 
manner. 


PERSPECTIVE  SKETCHING  43 


PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  3 

Curved  Strokes.  The  oval  of  the  numeral  0  is  the  basic  form 
for  the  6  and  9.  In  making  the  outline  strokes  of  these  numerals 
the  student  should  have  in  mind  the  form  of  the  complete  oval. 

Whole  Numbers  and  Fractions.  The  whole  number  in  a 
dimension  will  be  made  -J"  high. 

The  total  height  of  the  fraction  should  be  twice  the  height 
of  the  whole  number  with  a  clear  space  between  each  numeral 
and  the  division  line.  Fig.  141.  To  check  these  heights  mark 
off  an  eighth  inch  and  a  quarter  inch  space  on  the  edge  of  a  card 
and  use  it  as  a  scale.  Fig.  78. 


00000  104  520  500  214 1 
66666  460  506  672  276= 
99999  690  269  795  926= 

:1    '  .  JL     £     i!     11     Q!     c5      1^1      ppZ       L5— • 

4      ?     64      16       64       16       y2       DI6        IU2        ^^16         I6~ 

H 62-9^"— HH— |6-o{— H  Z 


FIG.  35.     LETTERING  PLATE  3.     0,  6,  9 


DATA  TOR  LETTERING  PLATE  3 

Given:     Plate  3  to  reduced  size.    Fig.  35. 
Required:     To  majse  the  plate  to  an  enlarged  scale. 


44 


MECHANICAL  DRAWING 


DATA  TOR  EXTRA  DRAWING  PLATE 

Given:  The  dimensioned  sketch  of  a  wall  bracket,  Fig.  36, 
with  the  upper  surface  of  the  enclosing  solid  3J"  below  the  level 
of  the  eye. 

Required:  To  draw  the  wall  bracket  full  size,  with  the 
surface  as  shown  3J"  below  the  level  of  the  eye,  but  with  the 
longer  horizontal  edges  receding  toward  the  left  instead  of  toward 
the  right. 


FIG.  36.    WALL  BRACKET 


CYLINDRICAL  OBJECTS 
PREPARATORY  INSTRUCTIONS  FOR  DRAWING   PLATE   4 

The  Vertical  Measure  Cylinder.  As  stated  before,  the  cube 
is  the  basic  form  for  the  perspective  sketching  in  this  course.  To 
secure  a  measure  unit  for  cylindrical  objects  a  cylinder  is  in- 
scribed in  a  measure  cube  as  shown  in  Fig.  37.  The  cylinder  is 
therefore  one  inch  in  diameter  and  one  inch  long.  The  principle 


PERSPECTIVE  SKETCHING 


45 


of  foreshortening  makes  the  axis  of  the  cylinder  and  the  major 
axis  of  each  of  the  ellipses  representing  its  bases  slightly  less 
than  one  inch.  In  sketching,  these  differences  may  be  ignored. 
In  Fig.  38  these  distances  are  one  inch  in  length. 

The  following  is  an  analysis  of  a  cylinder  which  will  be 
referred  to  as  the  vertical  measure  cylinder: 

1.  The  distance  between  the  centers  of  the  ellipses  is  equal 
to  their  major  axes  or  one  inch.    A  B  =  C  C'  =  D  D'.    Fig.  38. 

2.  The  major  axes  C  C'  and  D  D'  of  the  ellipses  are  at  right 
angles  with  the  axis  of  the  cylinder.     These  lines  do  not  con- 


IE' 


FIG.  37.    VERTICAL  CYLINDER  IN- 
SCRIBED IN  A  MEASURE  CUBE 


FIG.  38.    VERTICAL  MEASURE 
CYLINDER 


verge,  since  they  represent  lines  at  right  angles  to  the  direction 
of  sight  of  the  observer.  See,  "Direction  of  Lines  in  Perspec- 
tive," page  11. 

3.  The  minor  axes  E  E'  and  F  F'  are  coincident  with  the  line 
representing  the  axis  of  the  cylinder. 

4.  Due  to  the  difference  in  level  of  the  upper  and  lower  bases 
the  minor  axis  F  F'  of  the  lower  base  is  greater  than  the  minor 
axis  E  E'  of  the  upper  base.    The  minor  axis  of  the  upper  base 
"nay  be  determined  for  any  level  from  the  scale  of  levels  discussed 
in  the  following  paragraph. 

The  half  length  of  the  minor  axis  of  the  lower  ellipse  may  be 
determined  by  drawing  F  H'  through  D',  converging  with  E  H. 

A  Scale  of  Levels.  The  left  half  of  Fig.  39  is  a  scale  of  levels 
showing  the  upper  base  of  a  measure  cylinder  at  levels  one-half 


46  MECHANICAL  DRAWING 

inch  apart.  It  is  evident  that  the  area  and  minor  axis  of  the 
ellipse  increase  with  the  distance  of  the  ellipse  below  the  level  of 
the  eye.  The  distance  below  the  level  of  the  eye  of  the  center  of 


HORIZON 


FIG.  39.     SCALE  OF  LEVELS 


each  circle,  Fig.  39,  is  indicated  by  the  numerals  at  the  left  of  the 
figure.  In  this  course  the  student  will  be  aided  in  determining 
the  level  for  the  perspective  of  a  cylindrical  object  by  referring 


PERSPECTIVE  SKETCHING 


47 


to  this  scale.    To  the  right  of  the  scale  is  shown  its  application  in 
representing  a  cylinder  at  different  levels. 

To  Draw  and  Test  an  Ellipse  Representing  a  One-Inch  Circle. 

1.  Draw  light  indefinite  lines  at  right  angles  to  each  other  to 
represent  the  axes  of  the  ellipse. 


ti 


FIG.  40.    TESTING  AN  ELLIPSE 

2.  On  the  line  representing  the.  major  axis  lay  off  on  either 
side  of  the  intersection  of  the  axes  one-half  the  diameter  of  the 
circle. 

3.  Refer  to  the  scale  of  levels ;  estimate  and  lay  off  the  minor 
axis. 

4.  Sketch  the  ellipse  lightly  and  freely,  drawing  correspond- 
ing parts  in  consecutive  order,  i.e.,  draw  the  long  sides  of  the 


FIG.  41.     CONCENTRIC  CIRCLES  IN  PERSPECTIVE 

ellipse  and  then  the  ends.  Compare  the  form  thus  secured  with 
the  corresponding  ellipse  in  the  scale  of  levels.  Care  should  be 
taken  to  avoid  sharp  or  blunt  ends. 

5.  Ordinary  defects  in  the  form  of  the  ellipse  should  be  de- 
tected by  examining  it  as  follows : 

a.  Turn  the  sheet  to  the  right,  to  tne  left,  and  upside 
down,  and  view  the  form  carefully  when  the  sheet  is  in 
each  of  these  positions. 


48  MECHANICAL  DRAWING 

* 

b.  Locate  two  points  as  A  and  B,  Fig.  40,  on  the  axis 
equidistant  from  0.  The  vertical  distances  from  these 
points  to  the  ellipse  should  be  equal.  Compare  these  dis- 


FIQ.  42.    SPLIT  CORE  Box — Axis  VERTICAL 

tances  and  make  the  necessary  corrections.  x  Likewise  lo- 
cate C  and  D  equidistant  from  0  and  compare  the  vertical 
distances  from  these  points  to  the  ellipse.  Make  the  nec- 
essary corrections  as  before. 


CONCENTRIC  CIRCLES  IN  PERSPECTIVE 


The  problem  of  drawing  two  concentric  ellipses  is  more  diffi- 
cult than  that  of  drawing  a  single  ellipse. 


PERSPECTIVE  SKETCHING 


49 


Fig.  41  shows  two  concentric  ellipses  inscribed  in  concentric 
squares  shown  in  perspective.  The  ellipses  therefore  represent 
circles.  '  On  account  of  foreshortening,  the  axes  of  the  ellipses  do 
not  coincide  with  the  line  representing  the  diameter  of  the  circles 
or  with  each  other.  In  most  cases  the  difference  is  so  slight  that 
it  may  be  ignored.  For  very  large  ellipses,  however,  the  construc- 
tion shown  in  Fig.  41,  where  the  major  axis  of  the  larger  ellipse  is 


FIG.  43.    SPLIT  CORE  Box — Axis  HORIZONTAL 


slightly  in  front  of  the  major  axis  of  the  smaller  ellipse,  must 
be  used. 

In  Figs.  42  and  43  the  major  axis  C  F  is  laid  off  equal  to  the 
diameter  of  the  circle,  as  in  the  case  of  the  ellipse  representing 
a  one-inch  circle.  Fig.  38.  A  one-inch  ellipse  should  be  drawn 
first  and  tested.  In  cases  where  the  major  axes  of  the  ellipses  are 
made  to  coincide,  the  half  length  of  the  minor  axis  of  a  larger  or 
smaller  ellipse  may  be  determined  as  shown  in  Figs.  42  and  43. 
C  D  is  drawn  through  C  parallel  to  A  B.  In  cases  where  the  axes 
do  not  coincide  the  line  corresponding  to  C  D  should  be  made  to 
converge  slightly  with  A  B. 


50 


MECHANICAL  DRAWING 

DATA  FOR  DRAWING  PLATE  4 


Given:  The  dimensions  ef  a  split  core  box  for  standard 
one-inch  cores,  which  consists  of  a  hollow  cylinder  split  into 
halves;  outside  diameter  2",  inside  diameter  V,  length  3". 

Required:  A  perspective  sketch  of  the  split  core  box  with 
its  axis  vertical  and  the  upper  base  3"  below  the  level  of  the  eye, 
Fig.  42,  or  any  similar  object  assigned  by  the  instructor. 


STROKES 


WIDTH 


Ml!" 


FIG.  44.    LETTERING  PLATE  4 

Instructions: 

1.  Draw  through  the  center  of  the  sheet  a  vertical  line  to 
represent  the  axis  of  the  cylinder.    All  lines  should  now  be  drawn 
freehand. 

2.  Through  points  1-J"  above  and  below  the  center  of  the  sheet 
draw  horizontal  lines  as  the  major  axes  of  the  ellipses  represent- 
ing the  ends  of  the  bushing.    The  minor  axes  will  coincide  with 
the  axis  of  the  cylinder.    Care  should  be  taken  to  make  the  angle 
between  these  axes  a  right  angle. 

3.  Draw  the  ellipse  representing  the  smaller  circle  in  the 
upper  end  of  the  core  box  at  the  required  level.     Refer  to  the 
scale  of  levels  tojestimate  the  major  and  minor  axes  of  the  ellipse. 
Draw  the  ellipse  with  these  axes  and  test  it  as  described  under, 
"To  Draw  and  Test  an  Ellipse,"  page  47. 

4.  Lay  off  the  major  axis  and  determine  the  length  of  the 
minor  axis  of  the  larger  ellipse  as  described  under,  "Concentric 
Circles  in  Perspective,"  page  48. 


PERSPECTIVE  SKETCHING      .  51 

5.  Only  one-half  of  the  larger  ellipse  representing  the  lower 
end  of  the  bushing  will  be  seen.    The  length  of  the  minor  axis 
of  this  ellipse  may  be  found  by  the  method  illustrated  in  Fig.  42. 
H  G  is  drawn  through  G  converging  with  E  F.    While  only  the 
lower  half  of  the  ellipse  will  be  needed,  the  complete  ellipse  should 
be  drawn  as  construction. 

6.  Complete  the  constructive  stage  of  the  sketch  by  drawing 
the  vertical  contour  elements  of  the  cylinder  which  join  the  ends 
of  the  major  axes  of  the  large  ellipses. 

7.  Erase  all  construction  lines  and  complete  the  sketch  in  the 
usual  manner. 


=  88888    418-   698    785    829  = 
=  33333     136    983    568   3921  = 

*-*H  j  j  n 

>'-2^"— H  H-  I69'-0|"H     JL_    JL     J_: 


FIG.  45.    LETTERING  PLATE  4.     8,  3 

PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  4. 

The  combination  of  ovals  in  the  8  serves  as  a  basic  form  for 
the  3.  In  making  the  curved  strokes  of  these  numerals  the  stu- 
dent should  have  in  mind  the  form  of  the  complete  oval. 

DATA  FOR  LETTERING  PLATE  4 

Given:     Plate  4  to  reduced  size.    Fig.  45. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


52 


MECHANICAL  DRAWING 


DATA  FOR  EXTRA  DRAWING  PLATE 

Given:  The  dimensions  of  a  picture  frame  as  shown  in 
Fig.  46. 

Required:  To  draw  the  picture  frame  as  though  it  were 
lying  on  a  table,  with  its  upper  surface  4"  below  the  level  of  the 
eye.  At  this  level  a  portion  of  the  bottom  of  the  hole  will  be 
visible. 


37 


P-Sfr 

FIG.  46.  PICTURE  FRAME  SECTION 


PREPARATORY  INSTRUCTIONS   FOR  DRAWING  PLATE   6 

The  Horizontal  Measure  Cylinder.  Fig.  47  shows  a  horizontal 
cylinder  inscribed  in  a  measure  cube.  This  cylinder  is  therefore 
one  inch  in  diameter  and  one  inch  long.  Due  to  foreshortening, 


FIG.  47.    HORIZONTAL  CYLINDER  IN- 
SCRIBED IN  A  MEASURE  CUBE 


FIG.  48. 


HORIZONTAL  MEASURE 
CYLINDER 


the  major  axis  of  the  nearer  base  is  slightly  less  than  one  inch, 
and  the  axis  of  the  cylinder  is  shorter  than  the  line  representing 
the  horizontal  edge  of  the  measure  cube. 

These  differences  are  so  slight  that  they  will  be  disregarded 
in  the  following  analysis  of  the  cylinder,  which  will  hereafter  be 
referred  to  as  the  horizontal  measure  cylinder.  Fig.  48. 


PERSPECTIVE  SKETCHING 


53 


Figs.  49  and  50  are  similar  to  Figs.  47  and  48,  respectively, 
but  show  a  horizontal  cylinder  at  a  different  level,  with  its  axis 
receding  to  the  right  instead  of  to  the  left. 

1.  Since  the  axis  of  a  horizontal  cylinder  in  45°  perspective 
always  extends  toward  a  vanishing  point,  the  inclination  of  the 
axis  indicates  the  level  at  which  the  cylinder  is  drawn.    Figs.  48 
and  50. 

2.  The  major  axis  of  the  bases  are  perpendicular  to  and  the 
minor -axis  coincident  with,  the  axis  of  the  cylinder  as  in  the 
vertical  measure  cylinder. 


FIG.  49.     HORIZONTAL  CYLINDER 
INSCRIBED  IN  A  MEASURE  CUBE 


FIG.  50.    HORIZONTAL  MEASURE 
CYLINDER 


3.  The  major  axis  of  the  nearer  base  is  equal  in  length  to  the 
diameter  of  the  cylinder,  or  one  inch.    The  major  axis  of  the  .far- 
ther base  is  shorter,  on  account  of  the  convergence  of  the  contour 
elements  of  the  cylinder. 

4.  The  distance  between  the  centers  of  the  bases  is  equal  to 
the  horizontal  receding  edge  of  the  measure  cube,  which  is  ap- 
proximately three-fourths  of  the  front  vertical  edge  of  the  cube. 
Since  the  major  axis  of  the  near  base  is  drawn  equal  to  the  front 
vertical  edge  of  the  measure  cube,  or  one  inch,  the  distance 
between  the  centers  of  the  bases  may  be  taken  as  three-fourths 
the  length  of  the  major  axis  of  the  near  base.    This  ratio  remains 
constant  for  all  ordinary  levels. 

5.  It  will  be  noticed  in  Figs.  48  and  50  that  the  minor  axes 
of  the  nearer  bases  are  practically  equal  to  the  distance  between 
the  centers  of  the  bases  or  three-fourths  of  the  major  axis  of  the 


54  MECHANICAL  DRAWING 

nearer  base.  When  the  nearer  ellipse  is  drawn,  the  half  length 
of  the  minor  axis  of  the  farther  ellipse  may  be  determined  by 
drawing  a  line  CD  through  D,  converging  with  AB.  Fig.  48. 
These  lines  do  not  converge  toward  a  point  on  the  horizon  line. 

DATA  FOE  DRAWING  PLATE  5 

Given:     The  Split  Core  Box  represented  in  Plate  4.    Fig.  43. 

Required:  To  draw  the  Core  Box  in  a  horizontal  position 
with  its  axis  4|"  below  the  level  of  the  eye,  or  any  similar  object 
assigned  by  the  instructor. 

Instructions: 

1.  Draw  through  the  center  of  the  sheet  a  line  in  the  direction 
of  one  of  the  vanishing  points,  to  represent  the  axis  of  the  cyl- 
inder at  the  required  level.    The  angle  of  inclination  may  be 
obtained  from  Fig.  22. 

2.  Refer  to  Fig.  23,  estimate,  and  lay  off  three  foreshortened 
inches  on  tne  axis.    One-half  of  this  length  should  fall  on  either 
side  of  the  center  of  the  sheet  to  locate  the  drawing  centrally  on 
the  sheet. 

3.  Draw  through  the  points  thus  determined  the  major  axes 
of  the  bases  at  right  angles  to  the  axis  of  the  cylinder. 

4.  Draw  the  ellipse  representing  the  nearer  end  of  the  Core 
Box  as  shown  in  Fig.  43.     C  F  is  made  equal  in  length  to  the 
outside  diameter  of  the  Core  Box,  2".    D  is  determined  by  draw- 
ing C  D  through  C  parallel  to  AB.    Test  each  ellipse  as  described 
under,  "To  Draw  and  Test  an  Ellipse,"  page  47. 

5.  From  the  ends  of  the  major  axis  of  the  larger  ellipse  draw 
contour  elements  converging  with  the  axis  of  the  cylinder  to 
determine  the  ends  of  the  major  axis  of  the  farther  base. 

6.  The  half  length  of  the  minor  axis  of  the  farther  base  may 
be  determined  as  shown  in  Fig.  43.     H  G  is  drawn  through  G 
converging  with  EF.    EF  and  HG  do  not  converge  toward  a 
point  on  the  horizon  line.     While  only  one-half  of  the  farther 
ellipse  will  show  in  the  finished  drawing,  a  better  result  will  be 
obtained  by  drawing  the  complete  ellipse  as  construction. 

7.  Erase   all   construction   lines,   including  the   axes  of   the 
ellipses,  and  finish  the  sketch  in  the  usual  manner. 


PERSPECTIVE  SKETCHING 


55 


PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  5 

Horizontal  and  Vertical  Strokes.  As  stated  under  Plate  1 
vertical  strokes  are  usually  made  downward  and  horizontal 
strokes  to  the  right. 


HIT 


FIG.   51.     SPACING   OF   ADJACENT  VERTICAL   STEMS 

The  direction  of  horizontal  and  vertical  strokes  must  be  exact. 
The  relative  width  of  the  letters  is  shown  in  column  4.  Fig.  52. 


STROKES 

1 

2 

3 

\ 

Illli 

6 

1 

M 

T 

I  !  Ill 

—  rrfrl  

i 

l> 

=M 

u 

rfrrrr 

Pic.  52.    LETTERING  PLATE 


Spacing.     In  this  and  the  following  plates  practice  in  mak- 
ing individual  letters  will  be  followed  by  practice  in  making 


56  MECHANICAL  DRAWING 

words.  In  order  that  the  lettering  may  present  a  good  appear- 
ance, it  is  as  important  that  the  letters  be  well  spaced  as  that 
they  be  properly  formed. 

Correct  spacing  depends  more  on  the  judgment  of  the  drafts- 
man than  on  any  rule  which  might  be  given.  However,  it  may 
be  said  that  as  a  rule  the  letters  should  appear  to  be  equally 
spaced. 


=  11111  I  I  I  I  I  1234567890  847  z 
zLLLLL  ILI  LIL  ILLI  ILI  LILz 
zTTTTT  LIT  TILT  TILL  LIT  = 
zHHHHH  HIT  LITH  THILL  ITz 

I  HILT     LITH      THILL     TILT      HIT    TILL    HILL 


FIG.  53.    LETTERING  PLATE  5.     I,  L,  T,  H 

For  this  style  of  letters  adjacent  vertical  strokes  should  be 
a  distance  apart  equal  to  one-half  the  width  of  the  H.  Example  : 
H  and  I,  Fig.  51.  Letters  of  irregular  form  should  be  placed 
at  such  a  distance  that  the  space  appears  equal  to  that  between 
the  H  and  I.  Example :  I  and  T,  Fig.  51. 

When  spacing  a  letter  the  beginning  of  the  first  stroke  should 
be  carefully  located. 

DATA  FOR  LETTERING  PLATE  5 

Given:     Plate  5  to  reduced  size.    Fig.  53. 
Required :     To  make  the  plate  to  an  enlarged  scale. 


PERSPECTIVE  SKETCHING 


DATA  FOR  EXTRA  DRAWING  PLATE 


57 


Given:  The  dimension  of  a  picture  frame  as  shown  in 
Fig.  46. 

Required:  To  draw  the  picture  frame  as  though  it  were 
hanging  flat  against  a  vertical  wall,  with  its  center  3"  below  the 
level  of  the  eye. 

EXTENSION  OP  PERSPECTIVE  THEORY 
PREPARATORY  INSTRUCTIONS  TOR  EXTRA  DRAWING  PLATES 

The  Measure  Cube  in  New  Positions.  In  the  preceding  plates 
the  measure  cube  was  drawn  at  different  levels,  but  always  with 
its  side  faces  at  45°  with  the  horizon. 


135 


45° 


PIG.  54.    DRAWING  A  CUBE  AT  ANY  ANGLE 

If  the  measure  cube  is  turned  with  its  side  faces  making  other 
angles  with  the  horizon,  the  number  of  positions  in  which  an 
object  may  be  drawn  will  be  increased. 

Fig.  54  shows  a  method  of  constructing  a  measure  cube  at 
any  level  and  with  its  side  faces  at  any  desired  angle.  The  steps 
in  the  construction  are  as  follows : 

1.  Draw  an  ellipse  representing  a  two-inch  circle  at  the 
required  level. 


58 


MECHANICAL  DRAWING 


2.  Draw  a  semi-circle  of  the  same  diameter  as  the   circle 
represented  by  the  ellipse,  with  its  center  at  the  center  of  the 
ellipse. 

3.  Mark  off  on  the  semi-circle  the  angles  which  the  faces  of 
the  cube  are  to  make  with  the  horizon.    These  angles  should  be 
90°  apart. 

4.  Vertical  lines  through  these  points  intercept  the  ellipse 
in  the  ends  of  the  nearer  edges  of  the  upper  face  of  the  cube. 
These  edges  meet  at  the  center  of  the  ellipse  which  is  the  upper 
front  corner  of  the  cube. 


FIG.  55. 


CYLINDER  INSCRIBED  IN  A 
MEASURE  CUBE 


FIG.  56.    MEASURE  CYLINDER 


5.  Make  the  front  vertical  edge  one  inch  long  as  in  45° 
perspective. 

6.  Complete  the  cube  by  drawing  the  remaining  edges  con- 
verging so  as  to  give  the  faces  of  the  cube  the  appearance  of 
squares.    It  will  be  noted  that  the  farther  edges  of  the  upper  face 
intersect  on  the  line  making  45°  with  each  of  the  side  faces. 

The  Measure  Cylinder  in  New  Positions.  Fig.  55  shows  a 
horizontal  cylinder  inscribed  in  a  measure  cube  with  its  side 
faces  at  other  than  45°  to  the  horizon.  This  cylinder  is  there- 
fore one  inch  in  diameter  and  one  inch  long.  Due  to  foreshort- 
ening, the  major  axis  of  the  nearer  base  is  slightly  less  than  one 
inch  and  the  axis  of  the  cylinder  is  shorter  than  the  line  rep- 
resenting the  horizontal  edge  of  the  measure  cube.  These  differ- 
ences are  so  slight  that  they  will  be  disregarded  in  the  following 
analysis  of  the  measure  cylinder.  Fig.  56. 


PERSPECTIVE  SKETCHING 


59 


1.  The  distance  between  the  centers  of  the  bases  is  equal  to 
the  horizontal  receding  edge  of  the  measure  cube.    This  distance 
will  be  shorter  as  the  angle  of  the  axis  of  the  cylinder  to  the 
horizon  increases. 

2.  The  major  axes  of  the  bases  are  perpendicular  to,  and  the 
minor  axis  coincident  with,  the.  axis  of  the  cylinder. 

3.  The  major  axis  of  the  nearer  base  is  equal  in  length  to 
the  diameter  of  the  cylinder,  or  one  inch.     The  major  axis  of 
the  farther  base  is  shorter  on  account  of  the  convergence  of  the 
contour  elements  of  the  cylinder. 


x.v-— 


FIG.  57. 


CYLINDER  INSCRIBED  IN  A 
MEASURE  CUBE 


FIG.  58.    MEASURE  CYLINDER 


4.  The'length  of  the  minor  axis  of  the  nearer  base  will  depend 
upon  the  angle  that  the  axis  of  the  cylinder  makes  with  the 
horizon.  Fig.  56  illustrates  the  case  in  which  the  minor  axis  is 
lengthened,  due  to  the  axis  of  the  cylinder  making  an  angle 
greater  than  45°  with  the  horizon..  Pig.  58  illustrates  the  case 
in  which  the  minor  axis  is  shortened,  due  to  the  axis  of  the  cylin- 
der making  an  angle  less  than  45°  with  the  horizon.  The  length 
of  the  minor  axis  for  other  positions  may  be  estimated  by  using 
Figs.  56  and  58  as  guides.  For  any  angle  the  axis  of  the  cylinder 
makes  with  the  horizon  the  length  of  the  minor  axis  will  remain 
the  same  for  all  levels.  When  the  nearer  ellipse  is  drawn,  the 
half  length  of  the  minor  axis  of  the  farther  base  may  be  deter- 
mined by  drawing  a  line  C  D  through  D,  converging  with  A  B. 
Figs.  56  and  58. 


60  MECHANICAL  DRAWING 

DATA  FOR  EXTRA  DRAWING  PLATE 
Given:     The  objects  shown  in  Figs.  59,  60,  61,  and  62. 


FIG.  59.    CONCRETE  BLOCK 


Required:     To  draw  one  or  more  of  the  above  objects  in 
positions  selected  from  the  following  table  by  the  instructor. 


FIG.  60.    NAIL  Box 

The  level  at  which  the  object  is  drawn  may  be  assumed  by  the 
student. 


PERSPECTIVE  SKETCHING 


61 


The  right  vertical  face  of  the  enclosing  solid  makes  one  of 
the  following  angles  with  the  horizon : 

1.  15°.  2.  30°.  3.  60°.  4.  75°. 

The  objects  should  be  centered  on  the  sheet  as  in  previous 
problems. 


FIG.  61.    BROOM  HOLDER 


REVIEW  QUESTIONS 

1.  (a)  What  is  the  horizon?     (b)   How  is  it  represented? 
(c)  What  is  its  relation  to  the  eye? 

2.  (a)  What  is  a  vanishing  point?    (b)  Where  is  it  located? 

3.  Where  do  parallel  horizontal  lines  appear  to  meet  in  per- 
spective ? 

4.  Do  vertical  lines  appear  to  converge  in  perspective  ? 

5.  (a)  What  is  meant  by  foreshortening?     (b)  Are  the  per- 
spectives of  equal  lengths  on  the  same  vertical  edge  equal? 
(c)  On  the  same  horizontal  edge?     (d)  Are  the  perspectives  of 
equal  vertical  lengths  at  different  distances  from  the  observer 
equal  ? 

6.  (a)  What  is  the  angle  of  inclination?     (b)  How  does  it 
vary? 


62 


MECHANICAL  DRAWING 


7.  (a)   In  what  position  on  the  drawing  board  is  the  paper 
fastened?     (b)   How  is  it  fastened? 

8.  Describe  in  detail  how  the  pencil  should  be  sharpened  for 
sketching. 

9.  (a)  What  is  the  position  of  the  hand  and  pencil  in  sketch- 
ing horizontal  lines?      (b)  Vertical  lines?      (c)    What  is  the 


c 


FIG.  62.    BIRD  HOUSE   (DIMENSIONED  PERSPECTIVE) 

essential  difference?  (d)  What  movements  are  made  to  produce 
the  line  ? 

10.  (a)  What  is  meant  by  constructive  stage?  (b)  Finish- 
ing stage  ? 

11  In  what  way  does  a  scale  of  levels  assist  in  making  a 
perspective  of  a  rectangular  object  ? 

12.  (a)  Where  are  all  vertical  measurements  laid  off  in  per- 
spective? (b)  Why? 


PERSPECTIVE  SKETCHING 

13.  How  are  horizontal  measurements  made  ? 

14.  Explain  what  is  meant  by  enclosing  solid. 


63 


FIG.  63.    BOOK  BACK   (DIMENSIONED  PERSPECTIVE) 

15.  (a)  What  is  a  measure  cube?     (b)   Why  is  it  called  a 
measure  cube  ? 


17 


FIG.  64.    FORM  FOR  TESTING  CONCRETE  PRISMS 

16.  Of  what  use  is  the  table  line  1 

17.  (a)  How  do  you  proceed  to  locate  the  drawing  centrally 
on  the  sheet? 


64  MECHANICAL  DRAWING 

18.  How  are  the  perspectives  of  the  inclined  lines  located? 


FIG.  65.     TOOTH  BRUSH  HACK 


FIG.  6G.     PEN  RACK 


19.  (a)  Give  the  proportions  of  the  vertical  measure  cylinder, 
(b)  The  major  axes  of  the  bases  are  at  what  angle  with  the  axis 
»of  the  cylinder? 


PERSPECTIVE  SKETCHING  65 

20.  How  does  the  difference  in  level  affect  the  appearance  of 
a  horizontal  circle  in  perspective? 

21.  Of  what  assistance  is  a  scale  of  levels  in  drawing  a  vertical 
cylinder? 

22.  How  is  the  ratio  of  the  minor  axes  of  two  ellipses  repre- 
senting concentric  circles  determined  ? 

23.  (a)   Give  the  proportions  of  a  horizontal  measure  cylin- 
der,   (b)  The  major  axes  of  the  bases  are  at  what  angle  with  the 
axis  of  the  cylinder?     (c)  What  is  the  relative  length  of  the 
major  and  minor  axes  of  the  nearer  base  ? 

DATA  FOR  EEVIEW  DRAWING  PROBLEMS 

^-^__ 
Given:     The  objects  shown  in  Figs.  63,  64,  65,  66. 

Required:  To  draw  one  or  more  of  the  above  objects  in  45° 
perspective.  The  level  at  which  the  object  is  drawn  may  be 
assumed  by  the  student. 


CHAPTER  II 

ORTHOGRAPHIC  SKETCHING 
PROSPECTUS 

In  this  chapter  the  work  of  the  preceding  chapter  will  be 
continued  in  order  that  the  value  of  the  perspective  sketch  as  an 
aid  in  interpreting  orthographic  views  may  be  apparent.  At  the 
same  time  more  general  application  will  be  made  of  perspective 
principles  and  additional  skill  acquired  in  representing  objects 
pictorially. 

It  is  the  chief  aim  of  this  chapter  to  familiarize  the  student 
with  the  method  of  representation  generally  used  in  working 
drawings.  By  the  time  the  work  of  this  chapter  is  finished  the 
student  should  be  able  to  read  drawings  of  ordinary  complexity 
as  well  as  to  make  freehand  orthographic  sketches  with  a  con- 
siderable degree  of  skill  and  confidence. 

PEEPAEATOEY   INSTRUCTION   FOE   DEAWING   PLATE   6 

Views.  In  perspective  sketching  the  object  is  viewed  from 
one  position,  so  chosen  as  to  show  its  three  general  dimensions  in 
one  view.  Such  a  means  of  representation  does  not  show  the  prin- 
cipal surfaces  of  an  object  in  their  true  form  and  proportion  or 
the  principal  edges  in  their  true  lengths. 

In  order  to  represent  the  principal  surfaces  of  an  object  in 
their  true  form  and  proportion  and  the  principal  edges  in  their 
true  length,  the  object  is  usually  viewed  in  two  or  more  direc- 
tions, viz. :  from  directly  in  front,  directly  above,  or  directly  from 
the  right  or  left.  Each  view  thus  secured  will  give  the  exact 
form  and  proportion  of  the  surfaces  and  the  true  lengths  of  the 
edges  toward  which  one  is  looking  perpendicularly.  Views  thus 
secured  are  known  as  orthographic.  In  mechanical  drawing 
orthographic  views  are  generally  used. 

66 


ORTHOGRAPHIC  SKETCHING 


67 


Fig.  69  shows  two  views  of  a  bench  stop.  The  view  marked 
TOP  represents  orthographically  what  is  seen  from  directly 
above  the  object  and  the  view  marked  FRONT  represents  what  is 
seen  from  directly  in  front  of  the  object.  The  top  view  shows 
two  general  dimensions  in  horizontal  directions,  viz. :  the  dimen- 
sion from  left  to  right  and  the  one  from  front  to  back.  The  front 


FIG.  67.    TYPE  PROBLEM.    PERSPECTIVE  OF  BENCH  STOP 


view  shows  the  horizontal  dimension  from  left  to  right  and  the 
vertical  dimension.  Thus  the  three  general  dimensions  are  given 
in  the  two  views  and  the  proportions  of  the  object  are  determined. 
Relation  of  Top  and  Front  Views.  It  should  be  clear  from 
the  above  statement  that,  one  of  the  general  dimensions,  viz.: 
the  horizontal  dimension  from  left  to  right,  is  common  to  the 
front  and  the  top  views.  For  this  reason  as  a  matter  of  con- 
venience in  making  and  interpreting  the  drawing  it  is  essential 
that  the  top  view  always  be  placed  directly  above  the  front  view. 


68 


MECHANICAL  DRAWING 


Under  this  condition  all  distances  from  left  to  right  may  be 
projected  from  one  view  to  the  other. 

"Reading"  the  Drawing.  To  form  a  mental  image  of  an 
object  the  relation  of  its  surfaces,  edges,  and  corners  as  repre- 
sented must  be  studied.  This  process  is  called  reading  the  draw- 
ing and  is  illustrated  under  the  four  following  headings:  (The 
present  discussion  is  confined  to  rectangular  solids.) 


FIG.  68.     TYPE  PROBLEM. 


CONSTRUCTIVE  STAGE  OF  THE  ORTHOGRAPHIC 
SKETCH 


Plane  Surfaces.     Fig.  69  represents  an  object  having  plane 
surfaces. 

1.  When  the  observer  is  looking  perpendicularly  at  a  surface 
it  appears  in  its  true  form  and  proportion.     Example:     The 
rectangular  top  surface  A  B  C  D  of  the  bench  stop,  Fig.  69,  is 
represented  in  its  true  form  and  proportion  in  the  top  view. 

2.  When  the  observer  is  looking  edgewise  at  a  plane  surface 
it  appears  as  a  straight  line.    Example  :    Line  E  F  is  the  front 
view  of  the  top  surface  A  B  C  D.    Fig.  69. 


ORTHOGRAPHIC  SKETCHING 


69 


Straight  Edges. 

1.  A  straight  edge  viewed  at  right  angles  to  its  length  shows 
as  a  line  in  its  true  length.     Example :     The  front  edge  of  the 
top  surface  of  the  bench  stop  shows  in  its  true  length  in  line  A  B 
in  the  top  view  and  in  line  E  F  in  the  front  view. 

2.  A  straight  edge  viewed  endwise  appears  as  a  point.    Exam- 
ple :    Point  F  is  the  front  view  of  the  edge  B  C.    Fig.  69. 


-JO 


I 

.i-E 


FRONT 


FIG.  69.    TYPE  PROBLEM.    FINISHED  SKETCH  OF  BENCH  STOP 


Corners.  A  corner  appears  as  a  point  when  viewed  from  any 
direction.  Example :  The  upper  front  corners  at  the  left  of  the 
bench  stop  are  represented  by  A  in  the  top  view  and  E  in  the 
front  view. 

Invisible  Edges.  Hidden  edges  or  hidden  surfaces  viewed 
edgewise  are  represented  by  dotted  lines  to  distinguish  them  from 
visible  edges  or  surfaces.  Example:  GH  in  the  top  view. 
Fig.  69. 


70 


MECHANICAL  DRAWING 


PROBLEMS  AND  QUESTIONS  ON  ORTHOGRAPHIC  PRINCIPLES 

The  student  should  test  his  knowledge  of  the  orthographic 
principles  just  stated  by  answering  the  following  questions: 
See  Fig.  70. 

1.  (a)  Where  is  the  front  view  of  the  horizontal  surface  9, 
10,  15,  16?    (b)  Of  10,  12, 13, 15?    (c)  Of  9,  11,  14,  16? 

2.  (a)  Where  is  the  top  view  of  the  horizontal  surface  5,  4? 
(b)  Of  8,1? 


9  10  II 

TOP 


FRONT 

FIG.   70.    REVIEW  PROBLEM 


3.  (a)  Where  is  the  top  view  of  the  front  vertical  surface 
1,  2,  3,  4,  5,  6,  7,  8?     (b)  Of  the  rear  vertical  surface  1,  2,  3, 
4,5,6,7,87 

4.  (a)  Where  is  the  top  view  of  the  vertical  surface  7,  8? 
(b)  Of  3,  4?    (c)  Of  5,  6? 

5.  (a)  Where  is  the  top  view  of  the  front  horizontal  edge 
2,3?    (b)  Of  7,  6? 

6.  (a)  Where  is  the  front  view  of  the  rear  horizontal  edge 
15,13?    (b)  Of  16, 14? 


ORTHOGRAPHIC  SKETCHING  71 

7.  (a)  Where  is  the  front  view  of  the  upper  horizontal  edge 
10,15?     (b)  Of  12,  13? 

8.  (a)  Where  is  the  top  view  of  the  edge  5?    (b)  Of  6? 

9.  (a)  Where  is  the  front  view  of  the  upper  front  corner  12  ? 
(b)  Of  9?     (e)  Of  the  upper  back  corner  15? 

10.  (a)  Where  is  the  top  view  of  the  front  corner  2?     (b) 
Of  5? 

The  Type  Problem.  In  each  of  the  following  problems  pre- 
sented for  solution  the  methods  to  be  employed  and  the  results 
to  be  obtained  will  be  illustrated  by  a  type  problem.  This  type 
problem  will  consist  of  two  parts : 

1.  A  drawing  of  an  object  similar  to,  and  represented  in  the 
same  manner  as,  the  one  given  for  solution. 

2.  A  solution  of  the  problem  corresponding  to  that  required 
of  the  student. 

Example:  Fig.  69  is  the  type  problem  for  the  first  ortho- 
graphic sketch.  Fig.  67  is  the  perspective  of  the  bench  hook 
shown  in  Fig.  69  and  corresponds  to  the  kind  of  a  drawing  the 
student  will  make  from  Fig.  71,  72,  or  73. 

Materials.  The  materials  used  for  the  plates  in  this  chapter 
are  the  same  as  those  used  in  perspective  sketching  (see  page 
15;  except  that  in  this  case  the  5H  pencil  will  be  used  for  both 
the  constructive  and  finishing  stages. 

Perspective  Sketches.  In  this  chapter  perspective  sketches 
will  be  drawn  preceding  the  orthographic  sketches  as  a  means  of 
interpreting  the  orthographic  views  and  at  the  same  time  to 
continue  the  practice  necessary  to  develop  skill  in  representing 
objects  in  perspective. 

DATA  FOR  DRAWING  PLATE  6 

Given:     An  orthographic  sketch,  Fig.  71,  72,  or  73. 

Required:  To  draw  a  45°  perspective  sketch  of  the  object 
shown  in  Fig.  71,  72,  or  73  as  assigned  by  the  instructor,  with 
the  upper  front  corner  of  the  enclosing  solid  3J"  below  the  level 
of  the  eye  or  any  similar  object  assigned  by  the  instructor. 


^1 

I 


p i  A 
=  I 


FIG.  71.    GAIN  JOINT 


"^-ICJ 

f 

1 

i 

-*—  .3"--^ 

_T 

~-irj 

\ 

jL 

~-!N   t 

^    T* 

,^n 

-^ 

. 

&£*& 

^/.Je-AwZ)**^ 

(72) 


FIG.  72.    SCOURING  BOARD 


ORTHOGRAPHIC  SKETCHING 


73 


Instructions  : 

Use  the  corner  marked  A  as  the  upper  front  corner  of  the 
object.  All  lines  of  this  drawing  are  to  be  made  freehand,  includ- 
ing the  light  lines  in  the  constructive  stage.  Omit  all  dimensions. 


F 


iff 


-ft*- 


k-                 d 

-  —  Kvl 

P 

-ICM 

L   „      _      _, 

ro 
! 

t  ^ 

FIG.  73.    CEMENT  FERN  JAR 


PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  6 

Inclined  Strokes.  Before  starting  an  inclined  stroke,  the  stu- 
dent should  sense  its  direction,  moving  the  pencil  between  its 
two  ends  without  touching  the  paper. 


DATA  FOR  LETTERING  PLATE  6 

Given:     Plate  6  to  reduced  size.    Fig.  75. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


74 


MECHANICAL  DRAWING 


PREPAEATOEY  INSTEUCTIONS  FOE  DEAWING   PLATE   7 

The  Constructive  Stage.  This  stage  in  orthographic  sketch- 
ing is  similar  to  the  constructive  stage  in  Perspective  Sketching 
described  on  page  18.  It  consists  of  drawing  all  lines  of  the 
sketch  lightly  and  full.  No  attempt  should  be  made  to  make 
the  lines  exactly  the  right  length  in  this  stage.  When  drawing 


1 


I 


STROKES 


r 


I 


IE: 


WIDTH 


E 


"inii" 


FIG.  74.  LETTERING  PLATE 


each  line  it  should  be  made  long  enough  to  give  all  necessary 
intersections  with  other  lines. 

By  this  time  the  student  should  have  gained  such  facility  in 
drawing  freehand  lines  that  he  will  not  need  the  rule  to  draw 
straight  lines. 

If  a  straightedge  is  used  at  all  in  this  chapter  it  should  be 
necessary  only  in  ruling  long  lines  in  the  constructive  stage  and 
in  locating  one  view  directly  opposite  another. 


ORTHOGRAPHIC  SKETCHING  75 

In  laying  out  the  views  of  an  orthographic  sketch  on  the  sheet, 
proceed  in  the  following  manner : 

1.  Referring  to  Fig.  68,  mark  off  tentatively  the  position  of 
the  extreme  right  and  left  of  each  view.    Shift  both  marks  to  the 
right  or  left,  if  necessary,  to  make  A  equal  B. 

2.  In  like  manner  mark  off  the  vertical  dimensions  of  each 
view,  leaving  a  space  between  the  two  views  proportional  to  that 
which  is  shown  in  the  figure.    This  distance  should  be  from  J" 


FFFFF  LIFT  FIFTH  FIT  IF  z 
EEEEE  FILLET  FILE  TELL  z 
NNNNN  FIN  NINETEEN  FIN  z 
MMMMM  ELEMENT  LIMIT  z 

FEET     TENTH     MILE     NINE     LIME     FILM       Z 


FIG.  75.    LETTERING  PLATE  6 

to  V.     Shift  all  marks  up  or  down  if  necessary  to  make  C 
equal  D. 

3.  Make  any  necessary  adjustments  in  the  general  propor- 
tions of  the  views. 

4.  In  proportioning  the  details  of  the  views,  a  comparison  of 
the  dimensions  of  each  detail  with  the  dimensions  of  the  views  in 
which  it  appears  will  aid  in  securing  good  results.     Example: 
In  the  front  view,  Fig.  69,  the  width  of  the  cleats  is  about  one- 
sixth  of  the  total  length  of  the  bench  hook  and  their  thickness  is 
twice  that  of  the  board  to  which  they  are  fastened. 


76 


MECHANICAL  DRAWING 


Finishing  Stage.  As  in  Perspective  Sketching,  the  finishing 
stage  consists  in  erasing  unnecessary  lines  made  in  the  construct- 
ive stage,  tracing  over  the  outline  of  the  drawing,  and  otherwise 
giving  it  a  finished  appearance.  The  student  should  proceed  as 
follows : 

1.  Erase  all  construction  lines  and  retrace  the  lines  of  the 
drawing,  using  a  5H  pencil. 

2.  Represent  all  invisible  edges  by  dotted  lines  which  are 
composed  of.-J"  dashes  with  •£$"  spaces  between  them.    The  ends 
of  the  dashes  should  be  made  definite  by  placing  the  pencil  on  the 


3i 

Tl 

r 

^ 

\* 

} 

ti 

LJ 

-J 


FIG.  76.    DOTTED  LINES 


paper,  moving  it  the  required  length,  and  then  removing  it  as 
nearly  as  possible  vertically  from  the  paper.  Fig.  76  shows  the 
correct  method  of  joining  dotted  lines  to  full  lines. 

3.  Place  the  dimensions  on  the  sketch  as  described  below 
under,  " Arrangement  of  Dimensions." 

Arrangement  of  Dimensions.  Dimensions  are  placed  on  a 
drawing  as  shown  in  Figs.  71  and  72  to  show  the  size  of  the 
object  represented  Only  those  dimensions  are  given  which  are 
necessary  to  determine  completely  the  size  of  the  object. 

An  over-all  dimension  is  one  which  shows  the  distance  from 
one  extreme  point  to  another.  Example :  The  five  inch  dimen- 
sion in  Fig.  71.  A  detail  dimension  is  one  which  shows  the  dis- 
tance between  two  points  on  some  part  or  detail  of  the  object. 
Example :  The  three  and  one-half  or  one  inch  dimension.  Fig.  73. 


ORTHOGRAPHIC  SKETCHING 


77 


When  detail  dimensions  and  a  dimension  representing  their 
sum  are  given,  they  should  be  grouped  in  parallel  lines.  The 
shorter  dimension  should  be  near  the  outline  of  the  object  to  avoid 
the  confusion  arising  from  the  crossing  of  lines.  Example :  Those 
below  the  front  view,  Fig.  69,  are  properly  arranged. 

The  Dimension  Form.  Fig.  77  shows  what  is  known  as  the 
dimension  form.  It  includes  all  of  the  elements  of  the  convention 
used  in  indicating  linear  dimensions  on  a  drawing.  The  following 
points  should  be  noted : 


SPACE 


T 

~—  |C\J 

r 

00 

8 

1         2 

to 

A'        ^5" 

\  E 

8      \ 

\EXTENSION   LINE 

.DIMENSION   LINE 


FIG.  77.    DIMENSION  FORM 


1.  Horizontal  dimensions  read  from  left  to  right. 

2.  Vertical  dimensions  read  from  the  bottom  toward  the  top 
of  the  sheet. 

3.  Extension  lines  begin  about  $V'  i'rom  the  outline  of  the 
object  and  continue  J"  beyond  the  arrowhead. 

4.  The  space  between  the  outline  of  the  object  and  the  nearest 
dimension  line  or  between  two  parallel  consecutive  dimension 
lines  is  about  1". 

5.  Arrowheads  are  placed  on  the  dimension  lines  at  their 
extreme  ends. 

6.  Arrowheads  are  composed  of  two  slightly  curved  lines  sym- 
metrical with  respect  to  the  dimension  line.    The  length  of  the 
arrowhead  should  be  about  i"  and  the  width  Ty.    Fig.  77.    The 


78  MECHANICAL  DRAWING 

strokes  for  arrowheads  pointing  in  different  directions  are  shown 
in  Fig.  28. 

7.  The  whole  number  in  the  dimension  figure  will  be  made 
4"  high. 

8.  The  total  height  of  the  fraction  in  the  dimension  figure  is 
twice  that  of  the  whole  number  with  a  clear  space  between  each 
numeral  and  the  division  line. 


8 


FIG.  78.    SHOWING  ACTUAL  HEIGHTS  OF  WHOLE  NUMBER  AND  FRACTION 

To  check  these  heights  of  numerals  in  a  dimension  figure,  mark 
off  an  eighth-inch  and  a  quarter-inch  space  on  the  edge  of  a  card 
and  use  it  as  a  scale.  Fig.  78. 

9.  The  dimension  figure  is  generally  located  centrally  in  the 
dimension  line,  which  is  broken  sufficiently  to  admit  it. 


DATA  FOR  DRAWING  PLATE  7 

Given:     Orthographic  sketches,  Figs.  71,  72,  and  73. 

Required:  To  make  an  orthographic  sketch  of  the  object 
shown  in  Fig.  71,  72,  or  73 ;  or  any  similar  object  as  assigned  by 
the  instructor,  on  a  9"x  12"  sheet. 

Instructions: 

1.  Draw  a  border  line  as  in  perspective  sketching. 

2.  The  rectangles  shown  about  the  drawing  in  Figs.  71,  72, 
and  73  are  proportional  to  the  size  of  the  9"x  12"  sheet  and  the 
border  rectangle.    The  over-all  lengths  of  the  view  of  the  sketch 


ORTHOGRAPHIC  SKETCHING 


:$: 


STROKES 


-v/ 


2t 


WIDTH 


FIG.  79.    LETTERING  PLATE 


79 


7 

KKKKK    KILN    KEEL    KINK 
YYYYY    KEY    FLY    KNEEL 
ZZZZZ    MIZZEN     ZENITH 
AAAAA    FALL    LATHE    LAY 

LAZY    METAL    KENT     KNIFE    KINK     KEY 


FIG.  80.    LETTERING  PLATE  7.    K,  Y,  Z,  A 


80  MECHANICAL  DRAWING 

should  bear  the  same  ratio  to  the  dimensions  of  the  sheet  as  the 
corresponding  dimensions  in  the  figure  bear  to  the  size  of  the  rec- 
tangle representing  the  sheet.  With  this  in  mind  proportion  the 
views  and  locate  them  centrally  on  the  sheet  as  previously 
explained. 

3.  Draw  in  the  details  and  finish  the  drawing  of  the  views 
as  usual. 

4.  Draw  in  the  extension  lines,  dimension  lines,  arrowheads, 
and  numerals  following  the  directions  given  under,  "Arrange- 
ment of  Dimensions,"  page  76. 


PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  7 

As  stated  under  Plate  6,  the  student  should  sense  the  direc- 
tion of  an  inclined  stroke  before  drawing  it. 

The  spacing  between  irregular  letters  should  appear  equal 
to  the  area  of  one-half  the  H.  Fig.  81. 

KEY  : 

FIG.  81.     SPACING  OF  IRREGULAR  FORMS 


DATA  FOR  LETTERING  PLATE  7 

Given:     Plate  7  to  reduced  size.    Fig.  80. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


PREPARATORY   INSTRUCTIONS   FOR   DRAWING  PLATE   8 

It  is  customary  to  draw  the  top  and  front  views  of  an  object 
when  these  views  will  show  the  form  and  proportions  satisfac- 
torily and  when  only  two  views  are  needed.  Some  objects  are  of 
such  a  form,  however,  that  a  front  view  and  a  view  from  one 
side  are  needed  to  determine  completely  the  form  of  the  object. 
The  particular  side  view  is  selected  which  will  represent  the 
object  by  the  use  of  the  least  number  of  dotted  lines.  Fig.  82 
represents  an  object  which  would  be  well  defined  bv  the  nap 


ORTHOGRAPHIC  SKETCHING 


81 


of  a  front  view  and  one  side  view.  The  right  side  view  would 
be  the  one  chosen  in  this  case.  Since  the  two  side  views  contain 
the  same  information,  if  one  is  given  the  other  may  be  drawn. 
As  previously  explained,  an  observer  sees  all  vertical  dimensions 
and  the  horizontal  dimension  from  left  to  right  in  the  front 
view.  All  vertical  dimensions  and  the  horizontal  dimensions 
from  front  to  back  are  seen  in  the  side  view. 

A  right  side  view  is  always  placed  directly  to  the  right  and  a 
left  side  view  directly  to  the  left  of  the  front  view.  This  is  done 
both  for  the  sake  of  convenience  in  making  and  reading  a  draw- 


LEFT  SIDE. 


fRONT 

FIG.  82.     BEVELER 


RI6HT  SIDE 


ing  and  because  an  observer,  when  viewing  an  object,  would, 
after  obtaining  the  front  view,  naturally  step  to  the  right  for 
a  right  side  view  or  to  the  left  for  a  left  side  view.  To  secure 
the  front  view  after  the  side  view  is  drawn,  or  to  secure  the  side 
view  after  the  front  is  drawn,  all  vertical  distances  may  be 
projected  from  the  first  of  the  two  views  drawn.  Fig.  82  shows 
the  front  view  and  the  two  side  views  of  an  object  in  their 
proper  relative  positions. 

Inclined  Surfaces.  Any  surface  which  is  at  right  angles  to 
the  line  of  sight,  when  an  object  is  being  viewed,  will  show 
in  its  true  form  and  size.  A  surface  which  makes  other  than  a 
right  angle  with  the  line  of  sight  is  called  an  inclined  surface. 
Such  surfaces  do  not  show  in  their  true  form  and  size.  Fig.  82 
represents  an  object  having  inclined  surfaces.  If  one  surface  is 


82 


MECHANICAL  DRAWING 


rectangular  and  two  of  its  edges  are  at  right  angles  to  the  direc- 
tion in  which  it  is  inclined,  as  in  the  case  of  the  surface  C  D  E  F, 
Fig.  82,  the  vertical  dimension  of  the  rectangle  representing  the 
surface  in  the  front  view  is  less  than  the  actual  width  of  the 
surface. 

The  inclined  surface  C  D  E  F  is  represented  by  the  inclined 
line  G  H  in  the  left  side  view.  G  H  is  equal  to  the  true  width  of 
the  surface.  G'H',  representing  the  same  surface  in  the  right 
side  view,  is  also  equal  to  the  true  width  of  the  surface.  It  must 
be  evident  from  a  study  of  Fig.  82  that  in  representing  any  rec- 
tangular inclined  surface  which  has  two  of  its  edges  at  right 
angles  to  the  line  of  sight,  the  dimension  represented  by  these 


FIG.  83.     CONSTRUCTION  FOR  ANGLES  AND  HIDDEN  CORNERS  (PERSPECTIVE) 

edges  will  show  in  its  true  length.  C  D  and  E  F,  perpendicular 
to  the  direction  of  sight  in  the  front  view,  show  the  true  length. 
of  the  rectangle  in  this  view. 

The  end  edges,  GH  and  G'H'  of  the  surface  C  D  E  F,  are 
perpendicular  to  the  direction  of  sight  in  the  side  views  and 
therefore  show  the  true  width  of  the  surface  in  these  views. 

Inclined  Edges.  A  straight  edge  which  is  not  at  right  angles 
to  the  direction  in  which  it  is  viewed  is  represented  by  a  line 
shorter  than  the  actual  length  of  the  edge.  Example :  The  end 
edges  of  the  surface  C  D  E  F  are  represented  in  the  front  view, 
Fig.  82,  by  lines  C  E  and  D  F.  These  lines  are  shorter  than 
the  actual  lengths  of  the  edges,  as  shown  by  lines  GH  and 
G'H'  in  the  side  views. 

In  sketching  an  angle  where  the  direction  of  the  edge  is  given 
by  dimensions  locating  two  points  on  the  edge,  the  line  represent- 


ORTHOGRAPHIC  SKETCHING 


83 


ing  the  edge  should  be  determined  by  laying  off  the  dimensions 
given  to  locate  the  points  on  the  line.  Where  the  dimension  is 
given  in  degrees  the  ends  of  the  inclined  lines  should  be  located 
by  estimating  the  lengths  of  the  legs  of  the  right  triangle  of 
which  the  inclined  line  is  the  hypotenuse.  Example :  The  length 
of  the  lines  A  B  and  A  C,  Fig.  83,  are  laid  off  to  determine  the 
direction  of  B  C.  For  a  45°  angle  A  B  and  A  C  represent  equal 
distances.  For  a  60°  angle  AB  is  roughly  T%  of  AC. 

In  determining  the  position  of  a  line  passing  through  an 
invisible  corner,  such  as  E  F,  Fig.  83,  make  a  construction  for 
the  invisible  corner  by  drawing  lines  B  E  and  E  G. 

The  student  should  test  his  knowledge  of  the  orthographic 
principles  just  stated  by  answering  the  following  questions: 


10 

LEFT  SIDE  FRONT 

FIG.  84.    REVIEW  PROBLEM 


PROBLEMS  AND  QUESTIONS  IN  ORTHOGRAPHIC  PRINCIPLES 
Refer  to  Fig.  84. 

1.  Where  is  the  side  view  of  the  inclined  surface  1,  2,  7,  8? 

2.  (a)   Is  line  1,  2  equal  to  the  true  width  of  the  inclined 
surface?     (b)  Where  is  its  true  length  shown?     (c)  Why? 

3.  Where  is  the  inclined  edge  1,  8  shown  in  its  true  length  ? 
Why? 

4.  (a)  Is  the  vertical  surface  11,  15  on  the  front  or  back  of 
the  object?  (b)  Why?   (c)  Where  is  it  shown  in  the  front  view? 

5.  Where  is  the  vertical  surface  14,  13  shown  in  the  front 
view  ? 


84  MECHANICAL  DRAWING 

6.  Where  is  the  horizontal  surface  13,  16  shown  in  the  front 
view? 

7.  Where  is  the  horizontal  surface  6,  7  shown  in  the  side  view  T 

8.  Where  is  the  vertical  surface  4,  9  shown  in  the  side  view  ? 


T 


'?— H 


FRONT 


RIGHT    END 


FIG.  85.    TYPE  PROBLEM.     HARDIE.     GIVEN  VIEWS 


DATA  FOR  DRAWING  PLATE  8 

Given:     Orthographic  sketches,  Figs.  88  and  89,  90  and  91. 

Required:  To  draw  a  45°  perspective  sketch  of  the  object 
shown  in  Fig.  88,  89,  90,  or  91,  or  any  similar  object  as  assigned 
by  the  instructor. 

The  upper  front  corner  of  the  enclosing  solid  is  2J"  below 
the  level  of  the  eye.  Use  the  point  marked  A  as  the  upper  front 
corner  of  the  measure  cube.  All  lines  of  this  sketch  including 
the  constructive  stage  should  be  made  entirely  freehand.  Omit 
all  dimensions. 


FIG.  86.     TYPE  PROBLEM.    HARDIE.    PERSPECTIVE  SKETCH 


r 

—  I(M 

L 


FIG.  87.    TYPE  PROBLEM.     HARDIE.     BEQUIRED  VIEWS 


(85) 


A  A 


FIG.  88.     SHEET  METAL  HOPPER 


4-    *1 


-N- 


(86) 


FIG.  89.     KNIFE  AND  FORK  Box 


18 


-3-6" 


Fia.  00.     BENCH 


3MC 


FIG.  91.    BOOK  RACK 


(87) 


STROKES 


ii: 


Eli- 


\      \ 


WIDTH 


D 


FIG.  92.     LETTERING  PLATE 


zVVVVV  VALVE  LEVEL  LEVEL 
zWWWWW  WYE  WHEEL  FEW 
zXXXXX  LYNX  FIX  EXTENT 
zUUUUU  MINIMUM  MAXIMUM 
=  JJJJJ  AJAX  JAM  FAULTY 


(88) 


Fio.  93.    LETTERING  PLATE  8.    V,  W,  X,  U,  J 


ORTHOGRAPHIC  SKETCHING  89 


DATA  FOR  LETTERING  PLATE  8 

Given:     Plate  8  to  a  reduced  size.     Fig.  93. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


PREPARATORY  INSTRUCTIONS  FOR   DRAWING   PLATE   9 

Dimensioning  Angles.  The  inclination  of  an  edge  or  surface 
is  commonly  determined  by  giving  dimensions  which  fix  two 
points  on  the  line,  usually  its  ends.  Example :  The  wedge  end 
of  the  hardie.  Fig.  85.  In  some  cases  it  is  desirable  to  give  the 
inclination  of  an  edge  or  surface  in  degrees.  In  this  case  the 
dimension  line  is  an  arc  with  its  center  at  the  intersection  of  the 
two  lines  forming  the  angle.  '  Example :  The  45°  angle  in  the 
end  of  the  bench.  Fig.  90. 

Solution  of  the  Problem.  Attention  is  called  to  the  fact  that 
in  the  following  "problems  the  student  is  required  to  draw  dif- 
ferent views  from  those  given.  Read  the  statement  of  the 
problem  carefully  before  starting  to  draw. 

DATA  FOR  DRAWING  PLATE  9 

Given:  Orthographic  sketches,  Figs.  88,  89,  90,  and  91, 
showing  the  front  and  left  side  of  each  of  the  objects. 

Required:  To  draw  the  front  and  right  side  views  of  the 
object  shown  in  Fig.  88,  89,  90,  or  91,  or  any  similar  object  as 
assigned  by  the  instructor. 

Instructions: 

1.  Block  in  the  views  of  the  object  as  described  on  page  75 
and  as  carried  out  in  Plate  7,  so  that  they  are  in  the  center  of  the 
sheet. 

2.  Complete  the  details  of  the  views  in  light  lines. 

3.  Trace  over  the  lines  as  explained  on  page  76,  making  them 
the  proper  weight. 

4.  Draw  in  the  dimension  lines  and  put  in  the  arrowheads 
and  figures  in  the  order  given  on  page  77. 


90 


MECHANICAL  DRAWING 


5.  Write  in  the  plate  number  and  name  as  usual.    Press  the 
paper  back  into  the  tack  holes. 


Tdb 


FIG.  94.    SPACING  OF  CURVED  FORMS 


STROKES 


$1 


^- 


3 


WIDTH 


Q 


Q: 
b: 


FIG.  95.    LETTERING  PLATE 


PEEPAEATORY  INSTRUCTIONS  FOE  LETTEEING  PLATE  9 


The  letter  0  is  wider  than  the  numeral  0. 

The  forms  of  the  Q,  C,  and  G  are  based  on  the  oval  of  the  0. 


ORTHOGRAPHIC  SKETCHING  91 

Spacing  Curved  Stroke  Letters.  As  stated  in  the  instruc- 
tions for  Plate  5,  the  area  included  between  the  contour  of  two 
adjacent  letters  should  appear  equal  to  the  area  of  one-half  of 
the  H.  When  a  vertical  stroke  and  a  curved  stroke  are  properly 
spaced  the  clear  distance  between  them  is  slightly  less  than  one- 
half  the  width  of  the  H.  Example:  The  I  and  0.  Fig.  94. 

The  clear  distance  between  two  curved  strokes  will  be  less 
than  that  between  vertical  and  curved  strokes.  Example:  The 
0  and  0  in  Fig.  94. 


zOOOOQ  ONYX    AVIATION  |  = 

fOQQQQ  QUAIL    ANTIQUITYz 

zCCCCC  CHEQUE     CONNECTION z 

zGGGGG  ENGINE    GAUGE    r-s^'z 

zDDDDD  LADLE    HEAD      FLOAT z 


FIG.  96.    LETTERING  PLATE  9.    0,  Q,  C,  G,  D 

When  spacing  a  letter  having  a  curved  outline  the  begin- 
ning of  the  first  stroke  should  be  carefully  located.  In  planning 
the  letter,  the  clear  space  between  it  and  the  previous  letter  should 
be  held  in  mind. 

DATA  FOE  LETTERING  PLATE  9 

Given:    Plate  9  to  reduced  size.    Fig.  96. 
Required:     To  make  the  plate  to  an  enlarged  scale. 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  10 

Objects  thus  far  sketched  for  which  orthographic  views  were 
drawn  have  had  plane  surfaces.  In  Plate  10  an  object  having 
cylindrical  surfaces  is  to  be  represented  orthographically. 


92 


MECHANICAL  DRAWING 


Cylindrical  Surfaces.     In  Fig.  97  an  object  having  cylin- 
drical surfaces  is  represented  by  orthographic  views. 

1.  The  outline  of  the  front  view  represents  cylindrical  sur- 
faces when  viewed  at  right  angles  to  their  axes. 

2.  A  simple  cylinder,  when  viewed  in  this  direction,  appears 
as  a  rectangle. 


L 


FIG.   97.     TYPE  PROBLEM.     GIVEN  VIEWS  OF  A  SHAFT  COUPLING 

3.  The  straight  lines  representing  the  bases  of  the  cylinder, 
A  B  and  C  D,  Fig.  97,  are  equal  in  length  to  the  diameter  of  the 
cylinder  and  represent  the  bases  of  the  cylinder  viewed  edgewise. 

4.  The  straight  lines  representing  the  contour  elements  of  the 
cylinder  AC  and  BD  are  the  elements  of  the  cylinder  which 
divide  the  visible  part  of  the  surface  from  that  which  is  invisible. 
They  are  viewed  at  right  angles  to  their  direction  and  are  there- 
fore shown  in  their  true  length.     See  page  81  under  "Inclined 
Surfaces. ' ' 

As  stated  in  discussing  the  representation  of  plane  surfaces, 
a  surface  viewed  edgewise  is  represented  by  a  line.    In  the  case 


ORTHOGRAPHIC  SKETCHING 


93 


of  a  plane  surface  the  line  representing  the  surface  is  a  straight 
line. 

When  a  cylindrical  surface  is  viewed  in  the  direction  of  its 
axis  the  observer  is  looking  at  the  surface  edgewise  and  it  there- 
fore appears  as  a  line,  which  in  this  case  is  a  circle.  Example : 
EFGH,  Fig.  97. 


FIG.  98.    TYPE  PROBLEM.    PERSPECTIVE  OF  A  SHAFT  COUPLING 

Circular  Edges. 

1.  A  circular  edge  viewed  at  right  angles  to  its  plane  shows 
as  a  true  circle.    Example :  E  F  G  H  in  Fig.  97. 

2.  A  circular  edge  viewed  in  the  direction  of  its  plane  shows 
as  a  straight  line  equal  in  length  to  the  diameter  of  the  circle. 
Example :  A  B  and  C  D  in  Fig.  97. 

The  student  should  test  his  knowledge  of  the  orthographic 
principles  just  mentioned  by  answering  the  following  questions : 
See  Fig.  102. 

1.  (a)  Where  is  the  left  end  view  of  the  cylindrical  surface 
3,4,11,  12?  (b)  Of  1,  2,  13,  14V 


94 


MECHANICAL  DRAWING 


2.  Where  is  the  front  view  of  the  cylindrical  surface  25,  26, 
27,28? 

3.  (a)  Where  is  the  circular  surface  1,  16,  15,  14,  shown  in 
the  end  view?     (b)  Where  is  the  surface  2,  3,  12,  13  shown  in 
the  end  view? 

4.  (a)  Where  is  the  circular  edge  6,  9  shown  in  the  end  view  ? 
(b)  Where  is  the  circular  edge  4,  11  shown  in  the  end  view? 

5.  What  surface  would  be  crosshatched  if  a  quarter  section 
were  made  cutting  on  the  lines  0,  17  and  0,  18  ? 

6.  What  surface  would  be  crosshatched  if  a  half  section  were 
made  cutting  on  the  line  17,  19  ? 

7.  (a)  Where  is  the  left  end  view  of  the  extreme  element 
3,  4?     (b)   11,  12? 


FIG  99.     HALF  SECTION.     QUARTER  SECTION.    ILLUSTRATED  IN  PERSPECTIVE 


DATA  FOR  DRAWING  PLATE  10 

Given:     Orthographic  sketches,  Figs.  103  and  104. 

Required:  To  draw  a  perspective  sketch  of  the  object 
shown  in  Fig.  103,  104,  or  any  similar  object  as  assigned  by  the 
instructor,  with  its  axis  vertical.  The  upper  end  of  the  object  is 
2J"  below  the  level  of  the  eye. 


FIG.   100.    TYPE  PROBLEM.    CONSTRUCTIVE   STAGE  OF  THE  ORTHOGRAPHIC 

SKETCH 


FIG.  101.    TYPE  PROBLEM.    FINISHED  SKETCH  OF  A  SHAFT  COUPLING 

(95) 


96 


MECHANICAL  DRAWING 


i      z 


5          6 


FIG.  102.    REVIEW  PROBLEM 


DRILL 


£><*, 


FIG.  103.    CYLINDER  HEAD 


ORTHOGRAPHIC  SKETCHING 


97 


PEEPAEATORY  INSTRUCTIONS  FOE  LETTEEING  PLATE  10 

The  first  two  strokes  of  the  P,  R,  and  B  are  exactly  alike. 
The  basic  form  of  the  S  is  a  combination  of  two  ovals.  When 
drawing  the  strokes  of  the  S  these  ovals  should  be  held  in  mind. 


FIG.  104.    SPRING  CASING 


DATA  FOE  LETTEEING  PLATE  10 

Given:    Plate  10  to  a  reduced  size.    Fig.  106. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


PEEPAEATOEY  INSTEUCTIONS  FOE  DEAWING  PLATS  11 

Objects  thus  far  drawn  have  been  shown  in  their'  complete 
form.  By  referring  to  Fig.  97  it  will  be  noticed  that  all  hidden 
contour  elements  are  represented  bv  dotted  lines.  When  there 


98 


MECHANICAL  DRAWING 


are  too  many  of  such  lines  they  tend  to  confuse  the  reader  of  the 
drawing. 

Half  Section.  If  an  object  is  represented  as  though  a  portion 
of  it  has  been  removed,  the  drawing  can  often  be  made  much 
clearer  because  of  the  reduction  in  the  number  of  dotted  lines. 


STROKES 


I 


I 


IP. 


$ 


S 

5 


WIDTH 


R 


FIG   105.    LETTERING  PLATE 

A  common  method  of  showing  a  part  removed  is  to  imagine  the 
object  cut  into  two  similar  parts  through  an  axis  of  symmetry. 
Fig.  99. 

The  cut  is  made  in  a  plane  at  right  angles  to  the  line  of  sight 
and  the  near  half  of  the  object  is  imagined  removed.  The 
observer  then  sees  the  cut  surfaces  of  the  remaining  half  in  their 
true  form  and  proportions.  The  view  thus  obtained  is  called  a 
half  section  view.  Example :  See  the  front  view.  Fig.  101. 


ORTHOGRAPHIC  SKETCHING  99 

It  should  be  noticed  that  a  part  of  the  object  is  imagined  re- 
moved only  in  the  drawing  of  one  view.  The  end  view,  Fig.  101, 
represents  the  complete  object. 

Quarter  Section.  Another  common  method  of  representing 
an  object  is  to  imagine  it  cut  on  two  planes  at  right  angles  to 
each  other  in  to  an  axis  of  symmetry.  Fig.  99.  One  of  the  cut 
surfaces  is  at  right  angles  to  the  line  of  sight  and  the  other  is 
parallel  to  it.  The  quarter  of  the  object  included  between  the 


PPPPP  PITCH  DIAM  PATCH z 
RRRRR  ROD  RULE  ARMATURE  z 
BBBBB  BEARING  BUILDER  BINZ 
SSSSS  SCREW  PISTON  FOR  4  = 
SCOTT  &  JONES  z 


FIG.  106.    LETTERING  PLATE  10 

two  cut  surfaces  is  considered  removed.  The  observer  then  sees 
the  cut  surfaces  in  one  plane  in  their  true  form  and  proportions, 
and  those  in  the  other  plane  appear  as  a  line.  Fig.  101.  The 
view  thus  obtained  is  called  a  quarter  section.  It  should  be 
rioted  here  again  that  a  part  of  the  object  is  imagined  removed 
only  in  the  drawing  of  one  view. 

Crosshatching.  The  cut  surfaces  in  the  section  view  are  rep- 
resented conventionally  by  crosshatching,  which  consists  of 
drawing  very  fine  parallel  lines,  equally  spaced,  over  a  surface 
represented  as  cut.  In  the  student  problems  the  lines  should  be 
drawn  about  -jV'  apart  and  at  an  angle  of  45°  with  the  hori- 
zontal. Both  the  distance  between  the  lines  and  the  angle  at 


100  MECHANICAL  DRAWING 

which  they  are  drawn  should  be  estimated — not  measured.  It  is 
suggested,  however,  that  after  drawing  the  first  few  lines  the 
student  check  the  spacing  with  a  scale.  The  angle  of  the  cross- 
hatch  lines  should  be  carefully  checked  in  a  corner  where  hori- 
zontal and  vertical  boundary  lines  meet  at  right  angles.  When 
the  distances  from  the  corner  to  each  end  of  the  same  Crosshatch 
line  are  equal,  the  angle  is  45°. 

Center  Lines.  A  line  which  represents  an  axis  of  symmetry 
is  called  a  center  line.  Center  lines  may  be  straight  or  curved. 
Of  the  straight  lines  there  are  two  classes,  principal  and  sec- 
ondary. A  principal  center  line  is  one  about  which  the  entire 
view  is  symmetrical.  Example :  A  C  in  Fig.  101.  The  principal 
center  lines  should  extend  about  -J"  beyond  the  outline  of  the 
view.  A  secondary  center  line  is  one  about  which  only  part  of 
the  object  is  symmetrical.  Example :  E  F,  Fig.  101,  is  the  center 
line  for  the  hole  only.  Secondary  center  lines  should  extend 
about  \"  beyond  the  outline  of  the  part  of  which  they  represent 
the  axes. 

A  circular  center  line  usually  passes  through  the  centers  of  a 
number  of  holes  grouped  at  a  certain  distance  from  a  central 
point.  It  is  not  quite  a  complete  circle.  Example :  See  left  end 
view,  Fig.  101. 

In  general,  every  circle  in  a  drawing  must  have  two  center 
lines  at  right  angles  with  each  other.  Example :  Lines  17,  19  and 
Id,  20.  Fig.  102.  When  one  of  the  center  lines  is  circular,  as  in 
the  ease  of  the  center  line  for  the  drilled  holes  in  the  end  view, 
Fig.  103,  the  other  center  line  is  at  right  angles  to  the  tangent 
of  the  circular  center  line,  it  the  center  of  the  hole.  This  line 
is  therefore  a  radial  line  from  the  center  of  the  circular  center 
line. 

Dimensioning  Cylindrical  Surfaces  and  Circles.  The  diam- 
eter of  a  cylinder  may  be  given  by  placing  the  dimension  on  a 
diameter  of  the  circle  representing  the  cylindrical  surface. 
Example :  See  Fig.  101.  It  may  be  given  between  extension  lines 
drawn  from  the  rectangular  view.  Example :  See  Fig.  101.  In 
this  case  the  dimension  figures  should  be  followed  by  a  D  or 
Diam.  to  indicate  that  the  dimension  is  a  diameter.  A  hole  to 
be  drilled,  cored,  or  bored  may  be  indicated  by  printing  the  word 


ORTHOGRAPHIC  SKETCHING  101 

showing  how  it  is  to  be  obtained  or  finished,  together  with  the 
dimension  and  arrow  pointing  to  the  hole.  The  word  and  the 
dimension  should  be  placed  in  an  open  area  near  the  hole  rep- 
resented. The  line  drawn  under  the  word  should  be  about  -fa" 
below  the  letters.  Example :  See  Fig.  101. 

To  Sketch  a  Circle. 

1.  Through  the  center  of  the  circle  draw  two  light  lines  at 
right  angles,  and  on  each  lay  off  points  at  a  distance  from  the 
center  equal  to  the  radius  of  the  circle. 

2.  Repeat  this  process  by  drawing  another  pair  of  lines  which 
make  45°  with  the  first  pair.     In  case  the  circle  is  large  other 
similar  lines  may  be  drawn  which  bisect  the  angles  made  by  the 
first  lines. 

3.  Sketch  in  the  circle  through  the  points  located  on  the 
several  lines.     This  should  be  done  with  great  care.     The  first 
lines  drawn  should  be  very  light. 

4.  When  the  circle  is  complete  observe  its  form  carefully  and 
true  it  up  by  erasing  and  redrawing  any  portion  which  is  untrue. 

5.  In  the  finishing  stage  the  corrected  light  lines  should  be 
traced  over  to  produce  a  line  of  the  proper  weight. 


DATA  FOR  DRAWING  PLATE  11 

Given:  Orthographic  sketches,  Figs.  103  and  104,  or  any 
similar  problem  selected  by  the  instructor,  showing  the  front  and 
right  end  views. 

Required :  To  draw  the  front  quarter  sectior  and  left  end 
views  of  the  objects  shown  in  Fig.  103,  104,  or  any  similar  ob- 
ject as  assigned  by  the  instructor. 

Instructions: 

1.  Proportion  the  views  on  the  plate. 

2.  Draw  the  principal  center  lines  for  the  circular  view. 
Draw  the  circles  in  the  following  order:     (1)   The  larger  circles. 


102  MECHANICAL  DRAWING 

(2)  Circular  center  line.    (3)   The  circles  representing  the  small 
holes. 

3.  To  draw  the  rectangular  view,  first  determine  its  vertical 
dimensions  by  projecting  from  the  end  view.    Complete  the  view. 

4.  Retrace  the  lines  as  in  the  finishing  stage,  giving  particu- 
lar attention  to  those  affected  by  the  section. 

5.  Draw  in  extension  and  dimension  lines  and  put  in  the 
dimensions.  ,  Finish  the  sketch  by  crosshatching  the  cut  surfaces. 
Care  should  be  taken  to  make  the  section  lines  parallel  to  each 
other  and  at  45°  to  the  horizontal. 


LETTERING  IN  INK 
PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  11 

The  following  is  a  list  of  the  materials  used  in  making  letter- 
ing plates  in  ink. 

1.  Tracing  Cloth,  4"  x  6"  sheets. 

2.  One  of  the  following  or  any  similar  pen  which  will  give 
satisfactory  results  may  be  used: 

303  Gillott's 

404  Gillott's 

XT     .,    J-Three  of  each. 
Spencerian  No.  1 

Lady  Falcon 

3.  Penholder. 

4.  Black  waterproof  drawing  ink. 

Square  one  of  the  three  by  five  inch  cards  on  the  board  and 
stretch  the  tracing  cloth  over  it  with  the  dull  side  up.  The  sur- 
face of  the  cloth  should  be  prepared  for  inking  by  being  rubbed 
with  chalk  dust.  All  superfluous  chalk  must  be  removed  to 
prevent  its  clogging  the  pen.  The  guide  lines  for  the  letters 
should  be  drawn  on  the  cloth  in  pencil.  When  the  plate  is 
finished  a  border  rectangle  should  be  drawn  and  the  sheet 
trimmed  to  3"x5".  Fig.  18.  The  space  outside  the  cutting 
lines  may  be  used  to  try  the  pen  on  during  the  process  of  let- 
tering the  plate.  A  pen  should  be  selected  which  will  give  a 


OKTHOGKAPH1C  SKETCHING  103 

width  of  line  suited  to  the  height  of  letters  to  be  made.  The 
proper  width  of  line  should  be  secured  with  but  little  spreading 
of  the  nibs  of  the  pen.  Fig.  14  illustrates  the  position  of  the  pen 

ROUGH   ROUND   RODS 
OHIO  CORLISS   ENGINE 

FIG.  107.    EXAMPLES  OF  WORD  SPACING 

in  the  hand  while  lettering.  Note  that  the  forearm  is  nearly 
parallel  to  the  vertical  strokes.  Vertical  strokes  should  be  made 
with  a  finger  movement.  In  making  the  horizontal  and  curved 
strokes  this  movement  is  combined  with  a  turn  of  the  wrist. 


Z  CLAMP  TENSION  WEIGHING  FIXED  Z 
Z  FULL  SIZE  YOKE  BLOCK  LOCOMOTIVE  Z 
Z  VALVE  MOTION  SCALE  FULL  SIZE  Z 

Z  ANGLE     TENSION   WEIGHING   FIXTURE" 
:   FULL    SIZE    CORE    REAM    PLATE  GIRDERZ 


FIG.  108.    LETTERING  PLATE  11 

To  fill  the  pen,  place  the  ink  on  the  under  side  by  means  of 
the  quill  attached  to  the  stopper  of  the  bottle.  The  stopper 
should  be  returned  to  the  bottle  since  the  ink  dries  rapidly. 

Composition.  In  this  and  the  following  plates  in  lettering, 
words  will  be  combined  into  phrases  and  sentences.  The  spacing 
of  words  plays  an  important  part  in  securing  a  good  general 


104  MECHANICAL  DRAWING 

/ 

effect  in  a  line  of  letters.  The  space  between  words  should  appear 
equal  to  three  times  that  between  letters  or  one  and  one-half 
times  the  width  of  the  H.  Adjacent  vertical  strokes  will  there- 
fore be  separated  by  a  space  one  and  one-half  times  the  width  of 
the  H.  The  clear  distance  between  two  words  having  vertical 
strokes  adjacent  to  a  curved  stroke  will  be  less  than  one  and 
one-half  times  the  width  of  the  H.  The  clear  distance  between 
two  words  having  adjacent  curved  strokes  will  be  still  less. 
Example :  See  Fig.  107. 

DATA  fOR  LETTERING  PLATE  11 

Given:     Plate  11  to  reduced  size.    Fig.  108. 

Required:  To  make  the  plate  to  an  enlarged  scale.  In  this 
plate  the  wording  of  the  titles  for  the  first  pencil  mechanical 
drawing  plates  is  used.  The  letters  are  approximately  the  height 
used  in  the  title. 


REVIEW  QUESTIONS 

1.  (a)  In   what   direction    does   one   look   at   an   object  in 
making  its  orthographic  views?     (b)   How  does  this  differ  from 
the  way  it  is  viewed  in  making  a  perspective  of  it? 

2.  (a)   How  many  general  dimensions  does  each  orthographic 
view  show?     (b)   How  many  orthographic  views  are  necessary  to 
show  three  general  dimensions? 

3.  (a)  What  is  the  position  of  the  top  with  reference  to  the 
front  view?     (b)  Why?     (c)  Which  general  dimension  is  com- 
mon in  the  top  and  front  views  ? 

4.  What  is  meant  by  "Reading"  a  drawing? 

5.  (a)  Under  what  condition  does  a  surface  appear  as  a  line 
in  a  view?     (b)  When  a  hidden  surface  is  viewed  edgewise  how 
is  it  represented? 

6.  (a)  When  is  a  plane  surface  snown  in  its  true  form  in  one 
view  and  as  a  straight  line  in  the  other?     (b)  When  is  a  plane 
surface  shown  in  less  than  its  true  size  in  one  view  and  as  a 
straight  line  in  the  other? 


ORTHOGRAPHIC  SKETCHING  105 

7.  (a)   When  is  a  cylindrical'  surface  represented  as  a  rec- 
tangle?    As  a  circle?     (b)  When  is  a  circular  surface  repre- 
sented as  a  straight  line  in  one  view  and  as  a  circle  in  the  other  ? 

8.  (a)  When  is  a  straight  edge  of  an  object  shown  in  its  true 
length  in  two  views?     (b)  When  in  its  true  length  in  one  view 
and  as  a  point  in  the  other?     (c)  When  in  its  true  length  in  one 
view  and  in  less  than  its  true  length  in  the  other  ? 

9.  How  are  the  corners  of  an  object  represented  ? 

10.  Describe  the  process  of  proportioning  the  views  of  an 
object  and  locating  them  centrally  on  the  sheet. 

11.  What  are  the  lengths  of  dashes  and  spaces  in  dotted  lines  ? 

12.  (a)  Illustrate  by  a  sketch  how  detail  and  over-all  dimen- 
sions are  grouped,     (b)  What  space  is  allowed  between  the  out- 
line of  the  object  and  the  nearest  dimension  line?     (c)  Between 
dimension  lines  ? 

13.  (a)   Where  is  the  right  side  view  placed  with  respect  to 
the  front  view?     (b)  Where  is  the  left  side  view  placed  with 
respect  to  the  front  view  ? 

14.  (a)  What  general  dimensions  of  an  object  are  shown  in 
the  right  side  view?     (b)   In  the  left  side  view? 

15.  What  determines  the  choice  between  a  right  and  left  side 
view  * 

16.  (a)  Why  is  an  object  sometimes  shown  with  a  part  re- 
moved?   (b)  Define  quarter-section.    Define  half -section,    (c)   Is 
the  part  cut  by  the  section  planes  shown  as  removed  in  both 
views  ? 

17.  (a)  What  is  the  purpose  of  crosshatching  ?     (b)  At  what 
angles  are  the  crosshatching  lines  drawn  ?    (c)  What  is  the  usual 
distance  between  crosshatching  lines? 

18.  (a)  What  is  a  principal  center  line?     (b)  A  secondary 
center  line  ? 

19    (a)  When  is  a  straight  center  line  used?     (b)  Circular 
center  line  ? 

20.  (a)  How  many  center  lines  must  be  drawn  for  each 
circle?     (b)  At  what  angle  to  each  other? 

21.  Illustrate   how   the   two   views   of    a    cylinder   may   be 
dimensioned. 


FIG.  109.     BEARING  CAP 


ft 


.M 


-'I 

LELFT  SIDE 


(106) 


FIG.  110.    VISE 


— » — 


FRONT 


R1C.HT 


FIG.  111.    TURNING  TOOL  HOLDER 


FIG.  112.  •  VALVE  BONNET 


(107) 


103 


MECHANICAL  DRAWING 


DATA  FOE  REVIEW  PROBLEMS 

Given:     An  orthographic  sketch,  Fig.  109. 

Required:  To -make  the  orthographic  sketch  shown  in  Fig- 
109  to  an  enlarged  scale. 

Given :  An  orthographic  sketch,  Fig.  110,  showing  the  front 
dnd  left  side  views  of  the  object. 

Required:  To  draw  the  front  and  right  side  views  of  the 
object  shown  in  Fig.  110. 


FJG.  112A.     DOVETAIL  CROSS  SLIDE 

Given:  An  orthographic  sketch,  Fig.  Ill,  showing  the  front 
and  right  side  views  of  the  object. 

Required:  To  draw  the  front  and  left  side  views  of  the 
object  shown  in  Fig.  111. 

Given:  An  orthographic  sketch,  Fig.  112,  showing  the  front 
and  left  side  views  of  the  object. 

Required :  To  draw  the  front  quarter  section  and  right  side 
views  of  the  object  shown  in  Fig.  112. 


ORTHOGRAPHIC  SKETCHING  109 

Given:  Orthographic  sketches,  Fig.  112A,  showing  the 
front  and  left  side  of  each  of  the  objects. 

Required:  To  draw  the  front  and  right  side  views  of  the 
object  shown  in  Fig.  112A  as  assigned  by  the  instructor. 


CHAPTER  in 

PENCIL  MECHANICAL  DRAWING 

PROSPECTUS 

In  this  chapter  orthographic  sketching  is  continued.  A  more 
general  application  of  the  principles  of  orthographic  drawing  is 
made.  This  is  done  principally  by  introducing  problems  requir- 
ing three  views  from  perspective  sketches.  It  is  the  chief  aim 
of  this  chapter  to  give  considerable  practice  with  some  of  the 
common  instruments  and  materials  used  in  making  mechanical 
drawings  and  to  fix  a  standard  of  technique.  When  the  work  of 
this  chapter  is  completed,  the  student  should  be  able  to  make 
neat,  accurate  mechanical  drawings  of  simple  objects.  The  tech- 
nique of  the  lettering,  arrowheads,  and  figures  should  be  of  a 
standard  comparable  with  that  secured  in  the  mechanical  line 
work. 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE   12 

Three-view  Problems.  From  the  principles  developed  in 
Chapter  II  it  is  evident  that  each  view  shows  two  of  the  general 
dimensions  of  an  object  and  therefore  only  two  views  are  neces- 
sary to  obtain  all  three  of  the  general  dimensions  of  any  object. 
However,  in  some  cases  all  of  the  general  dimensions,  length, 
height,  and  thickness  may  be  given  and  still  the  form  of  the  ob- 
ject will  not  be  clearly  defined.  When  this  is  true  a  third  view  is 
necessary.  A  top,  front,  and  side  view  are  drawn  with  the  top 
above  the  front  view  and  the  side  view  to  the  right  or  left  of  the 
front  view  as  in  the  problems  of  Chapter  II. 

Example:  The  front  and  side  views  of  the  part  of  a  Sash 
Joint  in  Fig.  113A  do  not  show  the  form  of  the  tenon.  Hence 
a  top  view  is  necessary.  Also,  the  front  view  is  necessary  to  show 
the  notch  in  the  tenon,  and  the  left  side  view  to  show  the  bead. 

As  stated  under  Plate  8,  the  right  and  left  side  views,  convey 

110 


PENCIL  MECHANICAL  DRAWING 


111 


the  same  information  and  therefore  either  may  be  drawn.  The 
one  is  usually  selected  which  requires  the  fewer  dotted  lines. 
Example:  Comparing  Fig.  113,  A  and  B,  the  right  side  view  is 
preferable  for  this  reason.  Ordinarily  the  right  or  left  side  view 
is  (drawn  opposite  the  front  view  In  some  cases,  however,  a 
better  arrangement  will  be  secured  by  placing  the  side  view  oppo- 


E 


r-1 


X 


FIG.  113.    RELATION  OP  FRONT,  TOP,  AND  SIDE  VIEWS 

site  the  top  view  instead  of  opposite  the  front  view.  Fig.  113, 
C  and  D.  In  this  case  the  views  are  so  related  that  horizontal 
distances  from  front  to  back,  which  are  common  to  the  top  and 
side  views,  may  be  projected  from  one  view  to  the  other. 

To  relate  properly  the  side  view  to  the  front  view  of  an  object, 
attention  should  be  given  to  the  following  conditions: 

1.  In  all  cases  the  side  views  of  the  front  surfaces  are  adjacent 
to  the  front  view  of  the  object.    Example :  M  N  and  0  P  in 
113  represent  the  side  views  of  the  front  surface. 


112 


MECHANICAL  DRAWING 


2.  In  securing  the  views  of  an  object,  one  should  never  move 
the  object  but  should  himself  move  from  the  position  taken  in 
securing  a  front  view,  viz.,  to  the  left,  to  secure  the  left  side  view 
or  to  the  right  to  secure  a  right  side  view. 

The  student  should  test  his  knowledge  of  the  orthographic 
principles  just  stated  by  answering  the  following  questions: 
See  Fig.  114. 

1.  (a)  Why  is  the  top  view  of  the  object  necessary  ?  (b)  The 
front  view?  (c)  The  right  side  view? 


_J 


1 

r-1- 

i 
-j  

1 

FIG.  114.     REVIEW  PROBLEM 

2.  (a)   Is  the  right  side  view  preferable  to  the  left  side  view  ? 
(b)  Why? 

3.  (a)  Where  is  the  near  horizontal  edge  5,  6,  shown  in  the 
top  view?    (b)   In  the  front  view? 

4.  (a)  Where  is  the  vertical  surface  5,  8,  shown  in  the  front 
view?  (b)  In  the  top  view? 

5.  (a)  Where  is  the  back  vertical  surface  1,  2,  3,  4,  shown  in 
the  side  view?    (b)    In  the  top  view? 

6.  Draw  the  right  side  view  opposite  the  top  view. 

7.  Draw  the  left  side  view  opposite  the  front  view. 

8.  Draw  the  left  side  view  opposite  the  top  view. 


PENCIL  MECHANICAL  DRAWING 


113 


FIG.  115.     TYPE  PROBLEM.     PERSPECTIVE  OF  SASH  JOINT 

In  this  chapter  an  orthographic  sketch  will  be  required  pre- 
ceding each  mechanical  drawing.     This  freehand  practice  will 


FIG.  116.     TYPE  PROBLEM.    CONSTRUCTIVE  STAGE  OF  PENCIL  MECH.  DRAWING 


•„?' 

-J 


1 

>>!•* 


PENCIL  MECHANICAL  DEAWING 


115 


develop  further  skill  in  orthographic  sketching  and  will  make 
the  student  familiar  with  the  problem.  As  a  result  time  will  be 
saved  in  making  the  mechanical  drawing. 


DATA  FOR  DRAWING  PLATE  12 

Given:     Perspective  sketches,  Figs.  118,  119,  and  120. 

Required:  To  draw  a  three  view  orthographic  sketch  of 
the  object  shown  in  Fig.  118,  119,  or  120,  or  any  similar  object 
with  dimensions,  as  assigned  by  the  instructor. 


FIG.   118.    MORTISE 


Instructions: 


1.  This  sketch  should  be  drawn  entirely  freehand.     Propor- 
tions and  distances  should  be  estimated — not  measured. 

2.  Consider  the  form  of  the  object  carefully  and  select  the 
views  to  be  drawn. 

.  3.  Compare  the  over-all  dimensions  of  each  view  and  block  in 
the  view  by  drawing  a  rectangle  the  sides  of  which  are  in  the 
proportions  of  the  over-all  dimensions  of  the  object  shown  in  this 
view.  Example :  In  Fig.  117  the  over-all  dimensions  of  the  object 
which  are  represented  in  the  front  view  are  3f"  and  If".  The 
length  of  the  sides  of  the  rectangle  are  therefore  drawn  in  the 


116 


MECHANICAL  DRAWING 


FIG.  119.     MILK  STOOL 


Fio.  120.    CONCRETE  FLOWER  Box 


PENCIL  MECHANICAL  DRAWING  117 

approximate  ratio  of  3  j  :1  j=2 :1,  or,  in  other  words,  the  length 
of  the  rectangle  is  twice  its  width.  The  length  of  the  top  view 
is  equal  to  the  length  of  the  front  view.  Its  width  is  about 
one-fourth  of  its  length.  The  height  of  the  side  view  is  equal  to 
that  of  the  front  view.  Its  width  is  about  one-half  of  its  height. 
4.  The  distances  from  the  views  to  the  border  line  above  and 
below  the  views  should  be  equal  and  the  distances  from  the  views 
to  the  border  lines  at  the  right  and  left  should  be  equal.  Use  the 
same  principle  for  placing  the  views  as  given  for  the  problems 
of  Chapter  II,  page  81. 


z  FOUNDATION    WASHER    COREZ 

Z  ENGINE    BED     SCALE    FULL    SIZE      BACK  Z 
Z  REST      24    TURRET    LATHE      SCALED" 

z  JOURNAL    BEARING    ELECTRICZ 

'RAILWAY    MOTOR    CAR    SCALE   HALF  SIZE! 


FIG  121.    LETTERING  PLATE  12 

5.  When  the  rectangles  are  properly  located,  sketch  in  lightly 
the  details  of  each  view,  proportioning  them  by  eye. 

6.  Complete  the  views  by  retracing  the  lines. 

7.  With  the  advice  and  suggestions  of  the  instructor,  select 
the  necessary  dimensions  and  then  draw  extension  and  dimen- 
sion lines,  arrowheads,  and  figures. 

DATA  FOR  LETTERING  PLATE  12 

Given:     Plate  12  to  reduced  size.    Fig.  121. 
Required:    To  make  the  plate  to  an  enlarged  scale. 


118  MECHANICAL  DRAWING 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  13 

The  following  is  a  list  of  materials  needed  in  making  the 
pencil  mechanical  drawing  in  this  chapter : 

1.  Drawing  board. 

2.  High-grade  paper  similar  to  Duplex  or  Cream,  11"  x  15" 
sheets. 

3.  T-square. 

4.  30°-60°  and  45°  triangles. 

5.  High-grade  5H  pencil. 

6.  Scale. 

7.  Bow  compass. 

8.  4H  compass  lead. 

9.  Pencil  pointer. 

10.  Eraser. 

11.  Erasing  shield. 

The  Drawing  Board.  The  best  boards  are  designed  to  pre- 
vent warping,  various  means  being  used  to  accomplish  this  end. 
Some  are  built  of  narrow  strips  glued  together;  others  have  a 
series  of  saw  cuts  running  lengthwise  with  the  grain  to  reduce 
the  transverse  strength.  Fig.  122.  Such  boards  are  made  rigid 
by  cleats  of  hard  wood  screwed  through  oblong  slots  fitted  with 
metal  bushings  to  the  back  of  the  board.  This  construction 
allows  the  board  to  expand  and  contract,  the  screws  sliding  in 
the  slots. 

For  accurate  work  it  is  necessary  that  the  edge  of  the  board 
against  which  the  head  of  the  T-square  is  placed  be  perfectly 
straight  and  that  the  face  of  the  board  lie  in  a  plane.  To  test 
the  edges  of  the  board,  place  on  each  a  standard  straightedge 
or  the  edge  of  a  T-square  blade  which  is  known  to  be  straight. 
An  edge  of  the  board  is  straight  if,  when  held  up  to  the  light, 
the  straightedge  is  in  contact  at  all  points. 

The  surface  of  the  board  may  be  tested  in  like  manner  by 
placing  the  straightedge  upon  it  in  various  positions. 

The  edges  and  surface  of  the  board  should  be  kept  free  from 
cuts,  scratches,  and  bruises.  The  board  should  not  be  subjected 
to  extremes  of  temperature  or  moisture. 


FE1STCIL  MECHANICAL  DKAWING 


119 


Drawing  Paper.  For  mechanical  drawing,  where  a  sharp, 
fine  line  is  to  be  produced  with  a  hard  pencil,  a  tough,  hard  paper 
should  be  used.  It  should  stand  considerable  erasing  without 
injury  to  the  surface.  It  should  not  become  brittle  or  discolored 
from  reasonable  exposure  or  age.  If  freehand  lettering  is  to  be 
done  the  surface  must  be  reasonably  smooth  to  secure  the  best 
results.  If  considerable  time  is  to  be  spent  on  a  drawing,  a 


FIG.  122.    DRAWING  BOARDS 


paper  should  be  selected  which  has  an  agreeable  tint  and  which 
will  not  soil  easily  with  handling.  The  paper  used  for  the 
mechanical  drawings  of  this  course  must  fulfil  these  requirements. 

The  drawing  paper  should  be  fastened  to  the  board  in  the 
upper  left  corner  of  the  board  as  for  sketching.  After  inserting 
the  first  tack,  make  the  upper  edge  of  the  sheet  horizontal  by 
means  of  the  T-square ;  stretch  the  sheet  and  insert  the  remaining 
thumb  tacks  in  the  usual  manner. 

The  T-square  is  used  to  draw  horizontal  lines  and  to  provide 
an  edge  against  which  the  triangles  are  placed.  It  consists  of  a 


120  MECHANICAL  DRAWING 

rule  called  the  blade,  attached  to  one  end  of  which  is  a  cross- 
piece  called  the  head.  Fig.  123.  The  head  is  sometimes  fastened 
to  the  blade  by  means  of  a  swivel,  so  that  the  blade  may  be  set 
at  any  desired  angle. 

T-squares  are  made  of  steel,  hard  rubber,  and  wood.  The 
steel  blade  is  the  most  accurate  but  tends  to  soil  the  drawing. 
For  ordinary  work  wooden  blades  are  preferable.  They  are 
usually  made  of  maple,  mahogany,  or  pearwood,  and  their  edges 
are  often  lined  with  hardwood  or  celluloid. 


FIG.  123.     T-SQUARE.    PLAIN  AND  SWIVEL,  HEAD 

The  celluloid  edges  make  it  possible  to  see  lines  near  the  one 
to  be  drawn  and  are  therefore  quite  convenient  when  joining 
lines  at  corners,  etc. 

The  upper  or  working  edge  of  tht  T-square  and  the  edge  of 
the  head  which  rests  against  the  drawing  should  be  perfectly 
straight.  The  edge  of  the  blade  may  be  tested  as  follows : 

1.  Draw  a  long  line  along  the  edge  of  the  blade. 

2.  Reverse  the  ends  of  the  blade  with  respect  to  the  ruled  line, 
keeping  the  same  side  up  and  bringing  the  same  edge  against  the 
ruled  line. 

3.  Draw  a  second  line  along  the  edge  of  the  blade.    If  the 
edge  of  the  blade  is  straight  the  two  lines  will  coincide.    Both 
the  head  and  the  blade  of  the  T-square  may  also  be  tested  by 
means  of  a  straightedge.     Since  the  T-square  is  used  only  for 
ruling  parallel  lines,  and  as  lines  at  other  angles  are  drawn  with 
the  triangles  in  combination  with  the  T-square,  it  is  evident  that 
the  accuracy  of  the  angles  beween  lines  drawn  with  the  T-square 


PENCIL  MECHANICAL  DRAWING 


121 


and  those  drawn  with  the  triangles  does  not  depend  upon  the 
angle  of  the  blade  to  the  head  of  the  T-square.  It  is  not  neces- 
sary, therefore,  that  the  edge  of  the  head  and  blade  be  exactly 
at  an  angle  of  90°  to  each  other. 

Care  should  be  taken  to  preserve  the  upper  edge  of  the  blade 
of  the  T-square  from  injury.  It  should  never  be  used  as  a  guide 
for  the  knife  in  cutting  paper.  When  using  the  T-square  the 
head  is  pressed  firmly  against  the  edge  of  the  board  with  the  left 


FIG.  124.    EULING  A  HORIZONTAL  LINE 


hand  as  shown  in  Fig.  124.  The  lines  are  always  drawn  along 
its  upper  edge. 

The  triangles  are  used  in  combination  with  the  T-square  for 
drawing  lines  at  certain  angles  to  the  horizontal.  They  are  used 
in  combination  with  each  other  for  drawing  lines  at  various 
angles  with  lines  which  are  not  horizontal. 

Triangles  are  made  of  steel,  wood,  hard  rubber,  or  celluloid. 
Steel  triangles  are  used  for  the  most  accurate  work.  Triangles 
made  of  wood  are  easily  injured  and  are  likely  to  change  their 
shape.  Those  made  of  celluloid  have  the  advantage  of  being 
transparent  and  are  more  generally  used.  For  accurate  work  it 
is  necessary  that  the  edges  of  the  triangles  be  straight  and  that 


122 


MECHANICAL  DRAWING 


the  angles  be  true.  The  edge  may  be  tested  by  the  method  given 
for  testing  the  T-square. 

Assuming  that  the  edge  of  the  T-square  has  been  found  to  be 
straight,  the  90°  angle  of  a  triangle  may  be  tested  as  follows : 

1.  Place  the  triangle  in  position  D,  as  shown  in  Fig.  126,  and 
draw  the  line  AB. 


FIG.  125.    EULING  A  VERTICAL  LINE 


2.  If  when  the  triangle  is  turned  over  into  position  C,  the 
vertical  edge  coincides  with  the  line  A  B,  the  angle  is  90° 

3.  When  the  90°  angle  of  the  45°  triangle  has  been  found 
true,  the  45°  angles  are  true  if  equal. 

Compare  the  two  45°  angles  as  follows,  Fig.  127 : 

1.  Place  the  triangle  against  the  T-square  and  draw  a  45° 
line. 

2.  Turn  the  triangle  over  so  that  the  other  45°  angle  comes 
into  the  position  previously  occupied  by  the  first.    If  the  edges 
of  the  triangle  coincide  with  the  line  drawn,  the  45°  angles  are 
equal. 

The  60°  angle  of  a  30°-60°  triangle  may  be  tested  as  follows: 

1.  Draw  a  horizontal  line,  A  B,  along  the  T-square.    Fig.  128. 

2.  Draw  a  60 6  line,  B  C,  along  the  edge  of  the  triangle  cross- 
ing the  horizontal  line. 

3.  Turn  the  triangle  over  and  draw  a  second  60°  line.  AC. 


PENCIL  MECHANICAL  DRAWING 


123 


completing  a  triangle.    If  the  triangle  formed  is  equilateral,  the 
60°  angle  is  true. 

The  lengths  of  the  sides  of  the  triangle  may  be  compared  by 
means  of  the  dividers.    When  the  edges  are  straight  and  the  90° 


/ 


FIG.  126.     TESTING  THE  90°  ANGLE 

\c 


L. 


O       O 
O O 


O 


FIG.  127.     TESTING  THE  45°  ANGLE 
FIG.  128.     TESTING  THE  30°  AND  60°  ANGLES 

and  60°  angles  are  found  to  be  true,  the  remaining  angle,  30°, 
will  also  be  true. 


124  MECHANICAL  DRAWING 

With  the  30°-60°  triangle,  lines  may  be  drawn  at  90°  to  the 


FIG.  129.    LINES  DRAWN 

WITH  THE  30°,  60° 

TRIANGLE 


FIG.    130.     LINES    DRAWN 
WITH  THE  45°  TRIANGLE 


FIG.  131.     LINES  DRAWN  WITH  A  COMBINATION  OF  THE  30°,  60°  AND  45" 

TRIANGLE 

horizontal  and  at  30°  or  60°  with  the  horizontal  to  the  right  and 
to  the  left.    Fig.  129.    With  the  45°  triangle,  lines  may  be  drawn 


PENCIL  MECHANICAL  DRAWING 


125 


at  90°  to  the  horizontal  and  at  45°  with  the  horizontal  to  the  right 
or  to  the  left.  Fig.  130. 

By  combining  the  two  triangles,  lines  may  be  drawn  at  15° 
or  75°  with  the  horizontal  to  the  right  and  to  the  left.  Fig.  131. 

Lines  parallel  to  any  given  line  may  be  drawn  by  placing  the 
two  triangles  in  contact  and  sliding  them  as  one  tool  until  an 
edge  of  one  coincides  with  the  given  line.  Fig.  132.  With 
triangle  A  held  firmly  in  place,  triangle  B  may  be  moved  along 
it  and  lines  drawn  parallel  to  the  given  line. 


FIG.  132.     LINES  DRAWN  PARALLEL  OR  PERPENDICULAR  TO  ANY  GIVEN  LINK 


Lines  perpendicular  to  the  given  line  may  be  drawn  along 
the  edge  of  triangle  B  which  is  at  90°  to  the  given  line. 

The  direction  in  which  lines  should  be  drawn  along  the 
triangles  is  shown  in  Figs.  129  and  130.  The  forearm  should 
always  make  a  right  angle  with  the  line  being  drawn. 

The  edges  of  the  triangles  should  not  be  cut  or  bruised.  If 
they  are  allowed  to  fall  on  the  floor  a  corner  may  be  blunted  and 
as  a  result  the  angle  will  not  be  true.  The  celluloid  triangles 
should  not  be  allowed  to  remain  bent  for  any  length  of  time, 
as  they  will  remain  permanently  so. 

Pencils.  For  mechanical  drawing  where  it  is  desired  to  pro- 
duce fine  sharp  lines,  a  hard  pencil  should  be  used  on  a  compara- 
tively smooth,  hard  surfaced  paper.  The  pencil  should  not  be 
sharp  enough  or  used  with  enough  pressure  to  crease  the  paper. 

The  5H  pencil  should  be  used  for  drawing  lines  mechanically. 


126 


MECHANICAL  DRAWING 


For  convenience  in  using  the  pencil  for  different  purposes,  it 
should  be  sharpened  at  both  ends.  One  end  is  used  for  ruling 
lines  and  the  other  for  laying  off  measurements.  The  ruling 
point  is  obtained  by  cutting  away  the  wood  to  expose  about  J" 
of  lead  and  by  rubbing  opposite  sides  of  the  lead  on  a  sandpaper 
pad  or  file  to  produce  a  wedge-shaped  point.  Fig.  133.  This 
point  is  used  for  ruling  continuous  lines.  The  measuring  point 
is  similar  to  the  conical  point  used  in  sketching  except  that  the 
point  is  sharper  in  order  that  very  accurate  measurements  may 
be  laid  off  with  it.  It  is  used  both  for  measuring  and  making 
dotted  lines. 

To  insure  accuracy  in  laying  off  measurements  from  the  scale, 
the  eye  should  be  directly  above  the  division  on  the  scale  from 


RULING   POINT 


MEASURING    POINT 


FIG.  133.    EULING  AND  MEASURING  JOINTS  OF  THE  MECHANICAL  DRAWING 

PENCIL 


which  the  dimension  is  to  be  laid  off.  Care  should  be  taken  to 
place  the  point  of  the  pencil  on  the  paper  exactly  opposite  the 
mark  on  the  scale.  The  pencil  should  be  revolved  upon  its  axis 
while  in  this  position  without  pressing  the  lead  into  the  paper. 
The  mark  left  by  the  pencil  should  be  a  small,  round  dot  just 
visible  to  the  eye. 

Ruling  Horizontal  Lines.  In  ruling  horizontal  lines  the  posi- 
tion of  the  hand  is  the  same  as  for  sketching  horizontal  lines. 
In  this  case,  however,  the  pencil  is  held  leaning  slightly  forward 
with  the  point  in  the  position  shown  in  Fig.  124.  The  line  is 
drawn  with  a  continuous  motion  to  the  right  with  the  tip  of  the 
fourth  finger  touching  the  T-square  to  steady  the  hand.  Fig.  124. 
The  forearm  should  always  be  at  right  angles  to  the  line  being 
drawn. 

Vertical  Lines  are  drawn  along  the  edge  of  a  triangle  which 
is  set  against  the  T-square  as  shown  in  Fig.  125.  Note  that  the 


PENCIL  MECHANICAL  DRAWING  127 

triangle  is  to  the  right  of  the  line.  The  line  should  be  drawn 
away  from  the  T-square  with  the  hand  and  arm  in  the  same 
relative  position  to  the  line  being  drawn  as  for  horizontal  lines. 
Scales  are  used  for  taking  measurements  and  laying  off  dis- 
tances. They  are  made  of  paper,  steel,  and  wood.  Ordinarily 
scales  are  made  of  boxwood.  There  are  two  general  forms,  the 
flat  and  the  triangular.  The  flat  scale  may  have  from  one  to  four 
graduated  faces  and  the  triangular  scale  from  four  to  six  gradu- 
ated faces.  The  graduations  are  placed  directly  on  the  wooden 
face  of  the  scale  or  the  face  is  coated  with  a  white  compound 
which  makes  the  graduation  easier  to  read. 


0369 


FIG.  134.    HEADING  THE  ARCHITECT'S  SCALE 

The  faces  of  the  scales  are  graduated  as  follows: 

The  Engineer's  Scale  is  divided  to  10,  20,  30,  40,  50,  and  60 
parts  to  the  inch.  It  is  full  divided,  i.  e.,  the  small  divisions  are 
marked  off  for  the  full  length  of  the  face.  - 

The  Architect's  Scale  is  divided  to  &,  JL,  ^  i}  a  i; .  j,  i;  i^ 
and  3  inches  to  the  foot.  The  edges  on  this  scale  are  open  di- 
vided, i.  e.,  only  the  portion  of  the  face  representing  one  foot 
is  subdivided  to  read  in  smaller  units.  One  face  of  the  scale  is 
usually  divided  into  TV'  f°r  its  full  length. 

To  illustrate  the  reading  of  the  architect's  scale,  consider  the 
edge  designated  by  a  figure  1  at  the  end.  Fig.  134.  This  indi- 
cates that  one  inch  on  this  scale  represents  one  foot.  The  inch 
to  the  right  of  the  0  at  the  right  end  of  the  scale  is  divided  into 
forty-eight  equal  parts  so  that  each  of  the  smaller  divisions  rep- 
resents \"  and  the  spaces  between  the  0,  3,  6,  and  9  represent  3" 
each.  To  the  left  of  the  0,  the  readings  1,  2,  etc.,  are  inches,  and 
therefore  represent  feet.  To  measure  off  2' — 4£"  to  the  right  of 
point  X,  place  the  2  opposite  the  point  and  read  four  and  one- 
half  inches  to  the  right  past  the  0.  In  case  it  is  desired  to  lay  off 


128  MECHANICAL  DRAWING 

this  distance  to  the  left  of  Y,  place  the  four  and  one-half  inch 
mark  opposite  Y  and  read  past  the  0  to  the  2. 

The  Proportional  Inch  Scale  is  divided  to  read  one-half  or 
one-fourth  inch  to  the  inch  and  has  one  face  divided  to  -fa"  for 
its  full  length.  The  open  divided  edges  are  read  in  the  same 
manner  as  the  architect's  scale.  The  difference  is  that  in  this 
case  the  large  divisions  represent  inches  instead  of  feet.  One  of 
the  large  divisions  is  subdivided  to  read  sixteenths. 

Drawing  Instruments.  In  beginning  mechanical  drawing  it 
is  important  that  the  student  have  a  good  set  of  instruments.  It 
is  difficult  to  define  a  "good"  set  of  instruments,  for  the  better 
grades  are  extensively  imitated.  The  student  should  be  guided 
in  his  selection  either  by  some  experienced  draftsman  or  by  the 
trademark  and  the  price  charged  by  a  reliable  dealer. 

A  good  set  of  instruments  differs  from  a  poor  one,  mainly, 
in  the  quality  of  materials  used,  correct  tempering,  and  good 
workmanship.  The  steel  of  the  pens  must  be  properly  tempered 
so  that  when  once  sharpened  the  points  will  remain  in  good  con- 
dition for  a  reasonable  time.  The  compass  and  dividers  must  be 
so  made  that  they  will  retain  their  alignment  and  adjustment 
when  handled  with  ordinary  care.  These  qualities  can  only  be 
definitely  determined  after  the  instruments  have  been  given  a 
fair  trial. 

To  secure  uniformly  satisfactory  results  in  drawing  it  is 
necessary  to  start  with  a  good  set  of  instruments  and  to  keep 
them  in  good  condition. 

The  Compass  is  used  for  drawing  circles  and  arcs  of  circles. 
Fig.  135.  The  better  grades  are  made  of  German  silver.  It  is 
important  that  a  compass  be  light  yet  rigid.  The  most  impor- 
tant part  of  the  compass  is  the  head  which,  in  the  modern  instru- 
ments, consists  of  two  discs  held  in  contact  in  a  fork  by  means 
of  pivot  screws.  By  adjusting  these  screws  the  pressure  between 
the  discs  is  regulated.  This  pressure  should  be  such  that  the 
legs  of  the  compass  may  be  opened  or  closed  without  springing 
them.  On  the  other  hand,  the  joint  should  be  tight  enough  to 
retain  the  setting  when  the  instrument  is  in  use. 

The  thing  of  next  importance  is  the  socket  joint  of  the  remov- 
able pen  and  pencil  parts.  These  are  made  in  various  forms. 


PENCIL  MECHANICAL  DRAWING  129 

They  usually  consist  of  a  shank  on  the  pen  and  pencil  parts 
which  fits  into  a  corresponding  socket  in  the  compass  leg.  The 
proper  position  of  the  shank  in  the  socket  is  insured  by  some 
device  such  as  a  feather  or  sharp  corner  on  the  shank  which  is 
matched  by  a  corresponding  slit  or  groove  in  the  socket.  These 
parts  are  made  to  clamp  together  with  a  thumb  screw  or  else  a 
bayonet  fitting  is  used. 


FIG.  135.    DRAWING  A  CIRCLE  WITH  THE  COMPASS 

The  legs  of  the  compass  should  move  in  the  same  plane.    To 
test  the  compass  for  alignment: 

1.  Place  the  parts  in  the  sockets. 

2.  Bend  the  legs  out  at  the  head,  and 

3.  Bring  the  joints  together,  as  shown  in  Fig.  136.     If  the 
points  are  exactly  together  the  joints  are  true. 

Before  using  a  compass,  the  needle  point  and  lead  should  be 
adjusted  as  follows: 

1.  Place  the  pen  in  the  compass  and  adjust  the  needle  point 
so  that  it  projects  slightly  beyond  the  nibs  of  the  pen. 

2.  Remove  the  pen. 

3.  Replace  the  pencil  and  adjust  the  head  so  that  it  is  slightly 
shorter  than  the  needle  point.     The  pen  and  pencil  parts  are 
now  interchangeable  without  adjusting  the  needle  point. 


130 


MECHANICAL  DRAWING 


In  using  the  compass  proceed  in  the  following  manner : 

1.  Place  a  4H  lead  in  the  compass  and  sharpen  it  to  a  narrow 
wedge,  in  width  about  one-half  the  diameter  of  the  lead. 

2.  Set  the  lead  so  that  it  projects  about  one-half  the  length 
of  the  needle  point  beyond  the  shoulder. 

3.  Draw  the  center  lines  of  the  circle  to  be  drawn  at  right 
angles  and  lay  off  the  radius  on  one  of  them. 


FIG.  136.    TESTING  THE  COMPASS 

4.  Grasp  the  compass  by  the  handle  between  the  thumb  and 
first  finger  of  the  right  hand.    Care  should  be  taken  to  place  the 
needle  point  exactly  at  the  intersection  of  the  center  lines. 

5.  Adjust  the  lead  to  the  exact  radius  and  draw  the  circle, 
rolling  the  handle  of  the  compass  between  the  thumb  and  finger. 

The  large  compass  should  not  be  used  for  circles  of  less  than 
f  "  radius.  For  very  large  circles  the  lengthening  bar  should  be 
inserted  between  the  leg  of  the  compass  and  the  pen  or  pencil 
point.  When  this  does  not  suffice  a  beam  compass  should  be  used. 

Dividers  are  similar  to  compasses  in  general  appearance.  The 
legs  terminate  in  sharp  steel  points.  The  dividers  are  used  for 
laying  off  distances  from  the  scale,  for  transferring  lengths,  or 
for  dividing  straight  or  curved  lines  into  any  number  of  equal 
parts. 


PENCIL  MECHANICAL  DRAWING 


131 


To  divide  a  line  into  any  number  of  equal  parts  with  the 
dividers,  proceed  as  follows:  (Assume  that  the  line  is  to  be 
divided  into  three  equal  parts.) 

1.  Open  the  dividers  to  what  is  estimated  to  be  one-third  the 
length  of  the  line. 

2.  Step  off  the  estimated  distance  three  times  on  the  line. 


FIG.  137.     STEPPING  OFF  WITH  THE  DIVIDERS 


3.  Adjust  the  dividers  to  one-third  the  error  making  the  dis- 
tance between  the  points  larger  or  smaller  as  the  case  may 
require. 

4.  Repeat  the  process  until  the  third  step  ends  exactly  at  the 
end  of  the  line.    In  taking  the  steps  the  dividers  are  held  by  the 
handle  between  the  thumb  and  first  finger  and  swung  alternately 
first  to  one  side  of  the  line  and  then  the  other  as  shown  in 
Fig.  137.    This  avoids  rolling  the  handle  in  an  awkward  position 
between  the  thumb  and  finger. 


132  MECHANICAL  DRAWING 

The  Bow  Pen,  Bow  Pencil,  and  Bow  Dividers.  The  bow  pen 
and  bow  pencil  are  used  to  describe  small  circles,  and  the  bow 
dividers  to  lay  off  small  distances.  They  have  the  advantage  over 
the  larger  instruments  that  they  retain  their  adjustment.  There 
are  two  forms  of  adjusting  devices,  as  shown  in  Fig.  138.  To 
make  large  adjustments  in  the  instruments  having  side  screws  the 
pressure  on  the  nut  should  be  relieved  by  pressing  the  legs  to- 
gether with  the  left  hand  while  the  nut  is  made  to  spin  with  the 
first  finger  of  the  right  hand. 


FIG.  138.    CENTER  AND  SIDE  SCREW  ADJUSTMENT  OF  Bow  INSTRUMENTS 

The  bow  compass  should  be  used  in  the  same  manner  as  the 
large  compass,  as  described  on  page  129. 

The  Eraser.  Ordinarily  a  medium  hard  eraser  such  as  the 
ruby  is  used  for  removing  pencil  lines  from  a  drawing.  A  soft 
flexible  eraser  is  very  satisfactory  for  cleaning  a  pencil  drawing 
without  erasing  the  lines.  When  erasing  lines  the  paper  near  the 
lines  to  be  erased  should  be  held  down  with  the  thumb  and  first 
finger  of  the  left  hand  to  prevent  it  from  crumpling. 

The  Erasing  Shield  is  used  to  protect  the  parts  of  the  draw- 
ing which  are  not  to  be  erased.  The  opening  in  the  shield  is 
selected  which  is  best  suited  to  expose  only  the  parts  to  be  erased. 
The  shield  is  held  in  position  on  the  drawing  with  the  thumb  and 


PENCIL  MECHANICAL  DRAWING  133 

first  finger  of  the  left  hand,  while  the  eraser  is  applied  with  the 
right.    Fig.  139, 

STEPS  IN  MAKING  A  MECHANICAL  DRAWING 

The  Border  Rectangle.  To  draw  the  border  rectangle,  proceed 
as  follows : 

1    Lay  off  y  from  the  upper  and  left  hand  edge  of  the  sheet. 

2.  Through  the  points  thus  located  draw  the  upper  and  left 
hand  sides  of  the  border  rectangle. 


FIG.  139.    USING  THE  ERASER  AND  SHIELD 

3.  On  these  lines,  and  from  their  intersection,  lay  off  14"  to 
the  right  and  10"  downward. 

4.  Through  the  points  thus  found  draw  the  remaining  sides 
of  the  border  rectangle. 

The  Enclosing  Rectangle.  In  mechanical  drawing  the  views 
are  located  centrally  by  calculating  the  position  of  a  rectangle 
in  which  they  may  be  inscribed.  In  this  course  the  distance 
between  views  should  not  be  less  than  f  "  or  more  than  1".  The 
student's  calculation  should  be  made  as  indicated  in  Fig.  140. 

Accuracy.  It  is  of  prime  importance  that  a  mechanical  draw- 
ing be  accurate.  Accuracy  depends  both  on  the  quality  and  con- 
dition of  the  instruments  and  materials  and  upon  the  skill  of 
the  draftsman.  All  straightedges,  angles,  etc.,  should  be  tested 
as  just  described.  When  the  tools  are  found  to  be  in  good  con- 
dition the  draftsman  should  take  great  care  to  lay  off  measure* 


*-&ordert.j 


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X 

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PENCIL  MECHANICAL  DRAWING 

merits  accurately,  and  draw  the  lines  exactly  through  the  poinL 
located.  It  is  always  well  to  place  the  point  of  the  pencil  in  the 
located  point,  bring  the  straightedge  up  to  the  pencil,  and  then 
draw  the  line,  being  careful  to  maintain  the  same  relationship 
throughout  between  the  pencil  and  the  straightedge. 

Errors  multiply  with  the  number  of  operations  involved, 
hence,  other  things  being  equal,  the  most  direct  construction  is 
the  most  accurate  one. 

Constructive  Stage.  In  this  stage  all  measurements  are  laid 
off  and  lines  drawn  lightly  and  of  indefinite  length.  This  is  what 
is  sometimes  known  as  the  blocking-in  stage.  When  using  the 
scale  make  as  many  measurements  as  possible.  Whenever  prac- 
ticable, consecutive  measurements  should  be  laid  off  with  the 
scale  in  one  position.  Be  as  systematic  as  possible  in  making 
measurements  and  in  using  the  T-square  and  triangles.  It  is  a 
good  plan  to  draw  as  many  of  the  horizontal  lines  as  may  be 
drawn  at  one  time,  beginning  at  the  top  and  moving  the  T-square 
downward.  In  like  manner  draw  vertical  lines,  several  at  a  time, 
moving  the  triangle  from  left  to  right.  The  lines  should  be 
drawn  long  enough  so  that  there  will  be  no  need  to  extend  them. 

No  distinction  is  made  between  visible  and  invisible  edges  in 
this  stage.  Fig.  116. 

Finishing  Stage.  In  this  stage  the  drawing  is  completed  as  it 
will  finally  appear.  First,  erase  all  lines  not  needed  in  the  fin- 
ished drawing  and,  second,  retrace  all  required  lines  with  a  care- 
fully sharpened  5H  pencil.  All  finished  lines  must  be  of  uniform 
width  and  shade.  They  must  be  ended  at  the  proper  points. 
The  lines 'should  be  drawn  in  the  following  order: 

1.  Horizontal  lines  beginning  at  the  top  of  the  sheet. 

2.  Vertical  lines  beginning  at  the  left  of  the  sheet. 

The  hidden  edges  of  the  object  should  now  be  represented 
by  so-called  dotted  lines,  which  in  reality  are  lines  made  up  of 
short  dashes  and  spaces.  The  dashes  are  -J"  long,  separated  by 
sV  spaces.  Fig.  76.  The  end  of  each  dash  can  be  made  distinct 
by  keeping  the  end  of  the  pencil  in  contact  with  the  paper  until 
the  end  of  the  line  is  reached.  The  pencil  should  be  placed  upon 
the  paper,  drawn  J"  on  the  paper,  stopped,  and  then  raised  in 
making  each  dash. 


136  MECHANICAL  DRAWING 

Dimensioning.  The  draftsman's  judgment  is  used  more  in 
dimensioning  than  in  any  other  part  of  the  drawing.  To  avoid 
mistakes  and  to  facilitate  the  work  of  the  mechanic,  only  neces- 
sary dimensions  should  be  given.  They  should  be  placed  in  such 
a  way  as  to  make  the  drawing  easily  read.  Cases  are  rare  where 
it  is  advisable  to  repeat  the  same  dimensions  on  different  views. 
Repeating  dimensions  adds  to  the  difficulty  in  checking  them  and 
when  changes  are  made  there  is  a  possibility  of  making  a  change 
in  one  place  and  not  in  another.  This  leads  to  confusion.  Plac- 
ing dimensions  in  obscure  and  out  of  the  way  places  should  be 
avoided.  "Whenever  possible,  dimensions  should  be  grouped  in 
such  a  way  as  to  make  their  relation  obvious.  It  should  not  be 
necessary  for  the  mechanic  to  do  any  calculating  to  obtain 
necessary  dimensions. 

No  doubt,  the  best  guide  to  follow,  in  placing  dimensions  on 
a  drawing,  is  for  the  draftsman  to  imagine  himself  in  the  me-, 
chanic  's  place  and  to  consider  the  operations  through  which  the 
object  must  go  to  become  a  finished  product.  With  this  idea  in 
mind  most  problems  in  dimensioning  will  be  solved  without  diffi- 
culty. For  example,  when  a  machinist  drills  a  hole  he  sets  the 
point  of  the  drill  at  its  center ;  hence  the  hole  should  be  dimen- 
sioned by  referring  its  center  to  some  surface,  line,  or  point  easily 
accessible. 

In  ordinary  working  drawings,  dimensions  are  usually  given 
in  inches  up  to  twenty-four  inches.  Above  twenty-four  inches 
they  should  be  given  in  feet  and  inches.  Examples :  23J",  2'-4J". 

For  all  ordinary  work,  fractions  in  dimensions  containing 
mixed  numbers  have  the  following  denominators :  2,  4,  8,  16,  32, 
64 ;  such  denominators  as  6  or  19  are  not  used.  When  very  small 
fractions  of  an  inch  are  necessary,  as  in  the  case  of  special  fits, 
etc.,  the  fractional  part  of  an  inch  may  be  expressed  in  decimals 
of  three  or  four  places.  Example :  5.006"  bore. 

Extension  and  Dimension  Lines.  The  extension  lines  and 
dimension  lines  should  be  drawn  in  the  order  suggested  for  the 
finishing  stage  of  the  pencil  drawing,  i.e.,  draw  all  horizontal 
lines  beginning  at  the  top  and  moving  downward,  then  draw  all 
vertical  lines  beginning  at  the  left  and  moving  toward  the  right. 
As  in  orthographic  sketching,  the  extension  lines  should  begin 


PENCIL  MECHANICAL  DRAWING  137 

about  sV"  from  the  outline  of  the  object  and  continue  -J"  beyond 
the  arrowheads.  The  space  between  the  outline  of  the  object  and 
the  nearest  dimension  line,  or  between  two  parallel  consecutive 
dimension  lines,  should  be  about  J".  Th3  extension  and  dimen- 
sion lines  in  pencil  should  be  of  the  same  width  and  shade,  as  the 


PIG.  141.     SHOWING  ACTUAL  HEIGHTS  OF  WHOLE  NUMBER  AND  FRACTION 

object  lines.  Center  lines  may  be  used  as  extension  lines,  but 
not  as  dimension  lines. 

The  Dimension  Figures  and  Notes.  If  a  drawing  is  to  present 
a  neat  appearance,  a  suitable  type  of  letter  and  figure  should  be 
used  for  all  notes  and  dimensions.  A  very  plain  letter  should  be 
selected;  one  that  can  be  drawn  with  reasonable  rapidity  and 
that  will  be  in  harmony  with  the  remainder  of  the  drawing.  It 
is  essential  that  a  standard  height  be  adopted  and  adhered  to  for 
all  notes  and  figures  on  the  drawing.  For  this  course  the  stand- 
ard height  for  the  whole  number  is  y  and  the  total  height  of  the 
fraction  J"  as  shown  in  Fig.  141.  Whenever  possible,  notes 
should  be  lettered  on  horizontal  guide  lines.  The  letters  should 
be  5y  high.  To  insure  uniform  heights  for  all  notes  the  distance 
between  the  ruled  guide  lines  should  be  accurately  laid  off  with 
the  scale  or  stepped  off  with  the  dividers. 

As  nearly  as  possible,  place  the  dimension  figures  in  the  cen- 
ter of  the  dimension  line,  leaving  a  convenient  free  space  for  the 
figures.  Whenever  a  center  line  interferes  with  the  dimension 
figures,  place  it  near  the  center  line  and  either  to  the  right  or 
left  of  it.  In  the  case  of  consecutive  parallel  dimension  lines 
where  the  dimension  figure  in  one  line  would  naturally  interfere 
with  the  dimension  figure  in  the  other  dimension  line,  the  dimen- 
sion figures  should  be  '  *  staggered ' ' ;  that  is,  one  dimension  figure 
should  be  placed  a  little  to  the  right  and  the  other  to  the  left  of 
the  center  of  the  dimension  line,  so  that  they  will  not  interfere. 
Example:  Fig.  147. 


138 


MECHANICAL  DRAWING 


Information  which  the  dimensioned  drawing  does  not  make 
clear  is  put  into  the  form  of  notes.  They  usually  relate  to  mate- 
rials, finish,  number  of  parts  needed,  etc.  Example :  See  note 
below  the  view.  Fig.  156. 

The  Title.  The  views  of  an  object  with  their  dimensions  and 
notes  do  not  convey  all  of  the  necessary  information.  A  title 
which  supplies  the  deficiency  is  therefore  added.  The  title  is 


I 

.! 

M« 

NAME 

OF  OBJECT  REPRESENTED 

f 

| 

1 

'-I* 

PLATE!  FILING  (STUDENTS!             ^rAi  F 

N'UMBER|NUMBER|lNITIAL5|                  DCALE. 

"n^-4- 

!_  »^     l|"     ^ 

FIG.  142.     DIMENSION  AND  POSITION  OF  ITEMS  IN  TITLE  BLOCK 

usually  placed  in  the  lower  right-hand  corner  of  the  sheet  so  that 
it  will  be  easily  accessible  when  the  drawing  is  filed. 


-t 


/tl   TAIL    STOCK  _^-&  J 
r-=  rf^-i      ., 

\^Z  12"  SPElEp    LATHE 


I   256I' 


256    AGS.  SCALE-FULL  SIZE 


b 


AIL  $TOCK 

l*=    . 

2"  SPEED    LATHE 
SCALE-FULL  SIZE         I 


FIG.  143.     SHOWING  METHOD  OF  BALANCING  THE  LINES  ix  THE  TITLE 

Various  elements  may  enter  into  the  title,  depending  upon 
the  character  of  the  drawing  and  the  use  to  be  made  of  it.  The 
following  items  are  usually  found  in  the  titles  of  commercial 
drawings  of  machines  or  structures: 


PENCIL  MECHANICAL  DRAWING 

1.  Name  of  part  or  parts  of  machine  or  structure. 

2.  Name  of  complete  machine  or  structure. 

3.  Manufacturer's  firm  name  and  address. 

4.  Drawing  number. 

5.  Date  of  finishing  drawings. 

6.  Scale  to  which  drawing  is  made. 

7.  Initials  of  draftsman,  tracer,  and  checker. 


139 




-               | 

NOTICE  TO  SHOP 

PC.  HO. 

»»TT.  NO. 

MATKNIAL- 

HBAT  TITMT. 

•CALC. 

Decimal  Dimen- 

iVi.intainod. 
On    Dimension* 

•  peeifiod  ±.010 
will   bo  allowed. 

3  *»**•'«» 
••Mr***  »».- 

GISKOLT  MACHINE  CO. 

MAOI89N.WI9.  

»»f-  

"ATI 

CH»«[  ..CO.O 

PIECE  NO. 

0*0.1.0 

THIS  DHAWINQ  IN  DESIGN  AND  DETAIL  10  OUN  PHOPCHTV 

«NO  MUST  NOT  •(  U«EO  EXCEPT  IN  CONNCCTION  WITH  OUH  WO*K 

ALL  MIONTS  OF  OCSIQN  OH  INVENTION  ARC  MCSCrWCD. 


LINK-BELT  COMPANY 


PHILADELPHIA 


CHICAGO 


INDIANAPOLIS 


SCALE 


ORDER  NO. 


K8TIMATK  NO. 


APPROVED  BY 


CHCCKCO  IV 


FIG.  144.    COMMERCIAL  TITLES 


The  titles  of  the  plates  given  in  this  chapter  will  be  much 
simpler  than  the  ordinary  commercial  title.  Figs.  142  and  143 
show  two  forms  of  title  suitable  for  this  course.  The  words  for 
each  title  in  this  chapter  will  be  given  below  the  figure  from 
which  the  drawing  is  made. 

The  relative  importance  of  the  items  of  a  title  is  shown  by 
the  varying  heights  or  weight,  or  both,  of  the  letters.  In  some 


140  MECHANICAL  DRAWING 

drafting  offices  a  rubber  stamp  is  used  on  the  pencil  drawing  to 
obtain  the  words  and  lines  that  are  common  to  all  drawings.  The 
same  words  and  lines  are  often  printed  on  the  tracing  cloth  in 
type.  Example :  Fig.  144.  The  style  of  letter  used  should  be 
plain  and  dignified,  whether  printed  in  type  or  drawn  freehand. 

The  Title  Block.  The  title  for  each  mechanical  drawing  plate 
in  this  course  will  be  placed  in  a  title  "block.  The  dimensions  for 
this  block  with  the  names  and  position  of  the  items  are  shown  in 
Fig.  143.  The  height  of  the  letters  and  spaces  between  lines  of 
letters  are  shown  in  Fig.  143. 

Balancing  a  Title.  It  is  essential  to  the  appearance  of  a  title 
that  the  lines  be  symmetrical  with  respect  to  a  vertical  center 
line.  Example :  Fig.  143  shows  a  title  properly  balanced. 

To  balance  the  title  proceed  as  follows: 

1.  Tack  a  piece  of  drawing  paper  to  the  board  opposite  the 
lower  right  hand  corner  of  the  sheet.     Fig.  143.     This  will  be 
referred  to  as  the  trial  sheet. 

2.  Draw  a  line  as  a  continuation  of  the  lower  border  line  on 
the  trial  sheet.    This  is  a  base  line  for  measurements. 

3.  Lay  off  on  the  trial  sheet  the  space  for  the  letters  as  given 
in  Fig.  143.    Extreme  accuracy  in  making  these  measurements 
is  necessary,  as  the  width  of  the  letters  varies  with  their  height. 
A  small  error  in  height  makes  the  letter  appear  much  too  large 
or  too  small. 

4.  Rule  each  guide  line  on  the  trial  sheet  and  the  drawing 
sheet  with  one  setting  of  the  T-square.    Care  should  be  taken  to 
draw  exactly  through  the  points  located.    Check  the  heights  of 
the  spaces  with  the  scale. 

5.  Letter  each  line  of  the  title  on  the  trial  sheet,  giving 
attention  to  the  proportion  of  the  letters  and  to  spacing.    Do  not 
try  to  balance  the  lines  on  this  sheet. 

6.  Locate  the  middle  point  of  each  line  on  the  trial  sheet. 

7.  Draw  the  vertical  center  line  of  the  title  through  the 
center  of  the  title  rectangle. 

8.  Cut  out  each  line  of  letters  from  the  trial  sheet  and  place 
it  above  the  space  in  which  it  is  to  be  lettered  on  the  drawing 
sheet,  with  its  middle  point  on  the  center  line  of  the  title. 


PENCIL  MECHANICAL  DRAWING 


141 


9.  Letter  each  line,  following  the  spacing  on  the  trial  line. 
The  result  should  be  a  perfectly  balanced  title. 

DATA  FOR  DRAWING  PLATE  13 

Given:     The  orthographic  sketch,  Plate  12. 
Required:     To  make   a  pencil  mechanical  drawing  from 
Plate  12. 

Instructions: 

1.  Test  the  drawing  board,  T-square,  and  triangles  as  ex- 
plained under  the  corresponding  headings  in  this  chapter. 


zBRUSH  HOLDER  BRACKETS 

~  PRESSURE    TUNNEL -CABLE   REEL      JIG  Z 

=  FULL  SIZE       HINGE     BRACKETS 

~  CASING    OIL    COVER       OPERATING    CAM    Z 

z CLUTCH    LEVER    BRACKETS 


FIG.  145.    LETTERING  PLATE  13 

2.  Draw  the  border  line  as  previously  explained. 

3.  Calculate  the  size  of  the  enclosing  rectangle. 

4.  Lay  off  as  many  of  the  dimensions  of  the  object  as  possible 
at  one  time.    Draw  the  lines  lightly. 

5.  Check  the  drawing  for  accuracy. 

6.  Erase  unnecessary  lines  and  retrace  the  drawing,  taking 
care  to  end  the  lines  exactly  at  their  intersections.    Dot  the  lines 
representing  hidden  edges. 

7.  Draw  extension  and  dimension  lines  and  put  in  dimensions. 


142 


MECHANICAL  DRAWING 


8.  Letter  a  note,  giving  the  number  of  parts  required  and 
the  material  from  which  they  are  to  be  made. 

9.  Letter  the  title,  using  the  name  of  the  object  given  below 
the  figure  from  which  the  drawing  was  made. 

DATA  FOR  LETTERING  PLATE  13 

Given:    Plate  13  to  reduced  size.    Fig.  145. 

Required:     To  make  the  plate  in  ink  to  an  enlarged  scale 


FIG.  146.     TYPE  PROBLEM.    PERSPECTIVE  OF  BRACE 


PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE   14 

In  this  plate  the  student  will  need  to  decide  for  himself  the 
number  of  views  necessary,  and  their  arrangement,  to  show  the 
form  of  the  object.  It  is  suggested  that  for  this  purpose  he 
review  the  principles  given  on  pages  110  and  111. 


PENCIL  MECHANICAL  DRAWING 


143 


The  methods  of  dimensioning,  particularly  those  relating  to 
the  dimensioning  of  inclined  lines,  should  also  be  reviewed. 
Pages  136  and  137. 


FIG.  147.    TYPE  PROBLEM.    DETAIL  OF  BRACE  JOINT 


FIG.   148.    VISE  ANVIL 


DATA  FOR  DRAWING  PLATE  14 


Given:     Perspective  sketches,  Figs.  148,  149,  150,  and  151. 
Required:     To  draw  an  orthographic  sketch  of  the  object 


FIG.  149.    TOWEL  HANGER 


(144) 


FIG.  150.    FEED  HOPPER 


PENCIL  MECHANICAL  DRAWING 


145 


shown  in  Fig.  148,  149,  150,  or  151,  or  any  similar  object,  with 
dimensions,  as  assigned  by  the  instructor. 

Instructions:     Proceed  as  for  previous  orthographic  sketches. 


FIG.  151.    BIRD  HOUSE 

DATA  FOE  LETTERING  PLATE  14 

GiVen:     Plate  14  to  reduced  size.    Fig.  152. 

Required:     To  make  the  plate  in  ink  to  an  enlarged  scale. 


PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  15 

Inclined  Lines.  Lines  at  such  angles  as  15°,  30°,  45°,  60°, 
and  75°  may  be  drawn  with  the  T-square  and  triangles  described 
on  pages  123  and  124.  When  the  inclination  of  a  line  is  not 
given  in  degrees  at  least  two  points  on  it  must  be  located.  The 
line  is  then  drawn  by  placing  an  edge  of  a  triangle  or  the 
T-square  so  that  it  passes  through  the  two  points. 

Scale.  When  an  object  is  too  large  to  be  drawn  full  size  on 
the  sheet,  it  may  be  drawn  to  some  fraction  of  the  actual  size. 


146  MECHANICAL  DRAWING 

Half  and  quarter  sizes  are  common  scales  for  shop  drawings. 
The  edge  of  the  scale,  graduated  to  read  half  or  quarter  size, 
should  be  used  instead  of  dividing  the  dimensions  by  2  or  4. 
See  page  127  for  a  description  of  the  method  of  using  the  scale. 


BASE    PLATE    FOR  CABLE  REEL  z 

MOTOR  I  WANTED  -CAST  IRON  SCALE" 
QUARTER  SIZE  MANHOLE  FORZ 
CATSKILL  AQUEDUCT  CONDUIT  CAST  Z 
IRON  27  WANTED  SCALE-HALF  SIZE; 


FIG.  152.    LETTERING  PLATE  14 

DATA  FOE  DRAWING  PLATE  15 

Given:     The  orthographic  sketch,  Plate  14. 
Required:     To  make  a  pencil  mechanical  drawing  from 
Plate  14. 

Instructions: 

1.  Draw  the  border  line  and  calculate  the  size  of  the  enclosing 
rectangle  as  in  plate  13. 

2.  Lay  off  the  dimensions  of  the  object  and  complete  the  con- 
structive stage. 

3.  Check  carefully  each  dimension  for  accuracy. 

4.  Retrace  the  object  lines,   drawing    (1)    horizontal  lines, 
beginning  at  the  top;   (2)  vertical  lines  beginning  at  the  left; 
(3)  inclined  lines. 

5.  Draw  extension  and  dimension  lines  and  put  in  dimensions. 

6.  Letter  a  note,  giving  the  number  of  parts  required  and  the 
material  from  which  they  are  to  be  made. 


PENCIL  MECHANICAL  DRAWING  147 

7.  Letter  the  title,  using  the  name  of  the  object  given  below 
the  figure  from  which  the  drawing  was  made. 


=  CLUTCH    BRACKET    PRESSUREZ 

Z  TUNNEL    HOISTING    CAGE        2    WANTED  Z, 
Z   CAST     IRON       SCALE  -  QUARTER   SIZE    Z' 

z  MOTOR     BRACKET  FOR  VALVEZ 

I  OPERATING    MECH,     SCALE-HALF    SIZE! 


FIG.  153.    LETTERING  PLATE  15 
DATA  FOR  LETTERING  PLATE  15 

Given:     Plate  15  to  a  reduced  size.    Fig.  153. 

Required:     To  make  the  plate  in  ink  to  an  enlarged  scale. 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  16 

In  a  freehand  or  mechanical  drawing  where  a  straight  line  is 
tangent  to  an  arc,  the  arc  should  be  drawn  first.  In  the  con- 
structive stage  the  arc  should  be  drawn  long  enough  so  that  it 
will  extend  beyond  the  point  of  tangency  when  the  line  is  drawn. 
A  straightedge  may  then  be  laid  tangent  to  the  arc  and  the 
straight  line  drawn  in.  Before  the  drawing  is  finished  the 
unnecessary  part  of  the  arc  is  erased.  Fig.  155. 

Centers  for  rounded  corners,  fillets  and  other  arcs  of  circles, 
which  do  not  have  their  centers  on  any  line  of  the  drawing,  are 
located  by  what  is  called  the  "trial  and  error"  method.  The 
compass  should  be  first  adjusted  to  the  proper  radius.  To  locate 
the  center  of  the  arc,  set  the  lead  on  the  tangent  line  at  A,  Fig. 


148 


MECHANICAL  DRAWING 


FIG.  154.    TYPE  PROBLEM.    PERSPECTIVE  OF  BEARING 


FIG.  155.    TYPE  PROBLEM.    CONSTRUCTIVE  STAGE  OF  MECHANICAL  DRAWING 


150  MECHANICAL  DRAWING 

157,  estimating  A  C  as  nearly  as  possible  equal  to  the  radius  of 
the  arc.  Set  the  needle  point  at  B  opposite  A  and  bring  the  lead 
around  to  D.  Move  the  needle  point  parallel  to  A  C  an  amount 
equal  to  the  error.  The  compass  should  then  be  again  rotated 
back  to  A  to  test  for  accuracy,  and  if  necessary  further  adjust- 
ment should  be  made  before  drawing  the  arc. 


•4- 

i 


FIG.  157.     TRIAL  AND  ERROR  METHOD  OF  LOCATING  CENTERS 

Radius  Dimensions.  The  dimension  form  for  radius  dimen- 
sions is  shown  in  Fig.  189.  When  the  distance  between  the  arc 
and  its  center  is  great  enough  to  admit  the  figures  and  arrow- 
heads the  form  is  as  shown  in  Fig.  189.  Sometimes  a  small  cir- 
cle is  drawn  around  the  center  in  place  of  an  arrowhead.  This 
circle  should  be  made  freehand  and  about  TV'  in  diameter.  When 
the  distance  between  the  arc  and  its  center  is  short  the  center, 
as  shown  by  the  J"  radius,  is  not  indicated.  Fig.  189. 

DATA  FOB  DRAWING  PLATE  16 

Given:     Perspective  sketches,  Figs.  158,  159,  and  160. 

Required:  To  draw  an  orthographic  sketch  of  the  object 
shown  in  Fig.  158,  159  or  160,  or  any  similar  object,  with  dimen- 
sions, as  assigned  by  the  instructor.  The  student  should  decide 
what  views  are  necessary  to  show  the  form  of  the  object. 

Instructions:  In  drawing  the  circles  and  arcs,  sketch  in  the 
center  lines  and  lay  off  the  radii  on  each,  as  in  Plate  10. 

PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  16 

Composition.  This  and  the  following  plates  will  be  devoted 
to  the  practice  of  notes  which  frequently  appear  on  the  drawing 
to  give  information  not  shown  by  the  views. 


PENCIL  MECHANICAL  DRAWING 


151 


FIG.  158.    STUFFING  Box  GLAND 


FIG.  159.    STATIONERY  AND  INK  STAND 


152 


MECHANICAL  DRAWING 


DATA  FOR  LETTERING  PLATE  16 

Given:     Plate  16  to  reduced  .size.    Fig.  161. 

Required:     To  make  the  plate  in  ink  to  an  enlarged  scale. 


FIG.  160.     CLAMP 


DATA  FOR  DRAWING  PLATE  17 

Given:     The  orthographic  sketch,  Plate  16. 
Required:     To  make   a  pencil  mechanical  drawing  from 
Plate  16. 

Instructions: 

1.  Draw  the  border  line  and  enclosing  rectangle. 

2.  Locate  and  draw  two  center  lines  at  right  angles  to  each 
other  for  each  arc  or  circle. 


PENCIL  MECHANICAL  DRAWING  153 

3.  Draw  the  arcs  of  indefinite  length  so  they  extend  beyond 
the  points  of  tangency. 

4.  Draw  the  straight  lines  tangent  to  the  arcs. 

5.  When  the  constructive  stage  is  complete^  retrace  the  lines 
in  the  following  order :  (1)  circles  and  arcs ;  (2)  horizontal  lines, 
beginning  at  the  top  of  the  sheet;  (3)  vertical  lines,  beginning  at 
the  left  of  the  sheet;  (4)  inclined  lines. 


CORE    FOR    I"   FOUNDATIONS 

BOLT     BORE    2f"  FOR    2^"  SHAFT  FORZ 

12"  SHEAVE     COREZ 


Z  TAPPED    FOR    |"-ll    SET    SCREW      PIVOTZ 

zMILL    THIS    END    ONLY  TURNZ 


FIG.  161.    LETTERING  PLATE  16 

6.  The  center  line  may  be  produced  and  used  as  an  extension 
line  where  appropriate. 

1.  Letter  a  note,  giving  the  number  of  parts  required  and 
the  materials  from  which  they  are  to  be  made. 

8.  Letter  the  title. 


DATA  FOR  LETTERING  PLATE  17 

Given:     Plate  17  to  reduced  size.    Fig.  162. 

Required:     To  make  the  plate  in  ink  to  an  enlarged  scale. 


154  MECHANICAL  DRAWING 

REVIEW  QUESTIONS 

1.  (a)  What  determines  the  number  of  views  of  an  object? 
(b)  When  are  more  than  two  views  necessary? 

2.  Where  is  the  front  surface  of  an  object  represented  in  the 
side  view? 

3.  (a)  What  dimension  is  common  to  the  top  and  side  views? 
(b)  If  only  the  top  and  side  views  were  drawn  how  should  they 
be  related  ? 


zOPERATING  CAM  A  12  AS  z 
z  SHOWN  PATTERN  #117183  Lz 
z REVERSE  PATTERN  #819  Rz 

~  DRILL   FOR    {    ij    SPRING    COTTER    A.34Z 
I  CROWN    NUT    FOR    PIN    FOR    I&4      CORE! 


FIG.  162.    LETTERING  PLATE  17 

4.  What  are  the  requisites  of  a  good  drawing  board  ? 

5.  (a)  Describe  a  method  for  testing  the  surface  and  working 
edge  of  a  drawing  board,     (b)  What  care  should  be  taken  of 
the  surface  and  working  edge  of  a  drawing  board  ? 

6.  Give  requisites  of  a  good  T-square  and  explain  its  uses. 

7.  Is  it  necessary  for  the  head  of  a  T-square  to  be  at  right 
angles  to  the  blade  ?    Why  ? 

8.  Describe   a  method  for  testing  the  working  edge  of  a 
T-square  for  straightness. 

9.  (a)  Describe  the  position  of  the  T-square  for  drawing 
horizontal  lines,    (b)  How  is  it  held?    (c)  Illustrate  by  a  sketch 
the  position  of  the  pencil  in  ruling  a  line  along  the  T-square. 


PENCIL  MECHANICAL  DRAWING  155 

10.  Describe  the  process  of  squaring  and  fastening  the  paper 
on  the  board  for  a  mechanical  drawing. 

11.  What  is  the  advantage  of  the  celluloid  triangle  over  tri- 
angles made  of  other  materials  ? 

12.  (a)  For  what  are  triangles  used?     (b)  For  what  angles 
are  they  usually  cut  ? 

13.  Describe  a  method  of  testing  the  accuracy  of  a  90°  angle 
of  a  triangle. 

14.  Describe  a  method  of  testing  the  accuracy  of  a  45°  angle 
of  a  triangle. 

15.  Describe  a  method  of  testing  the  accuracy  of  a  30°  and 
60°  angle  of  a  triangle. 

16.  (a)  Show  by  a  sketch  how  to  construct  an  angle  of  15° 
with  a  horizontal  line  by  means  of  the  T-square  and  triangles, 
(b)  What  angle  does  this  make  with  a  vertical  line? 

17.  (a)  Show  by  a  sketch  how  to  construct  an  angle  of  75° 
with  a  horizontal  line  by  means  of  the  T-square  and  triangles, 
(b)  What  angle  does  this  make  with  a  vertical  line  ? 

18.  When  using  the  triangle  against  the  T-square  in  which 
direction  should  the  line  be  drawn?     (b)  Show  different  cases 
by  sketching. 

19.  Show  by  a  sketch  how  to  draw  a  line  parallel  to  any  given 
line  using  only  two  triangles.    Perpendicular, 

20.  (a)  Describe  the  positions  of  the  T-square  and  triangle 
for  drawing  a  vertical  line,     (b)  In  which  direction  is  the  line 
always  drawn  ? 

21.  (a)  What  is  the  shape  of  the  ruling  point  of  the  pencil? 
(b)   How  is  it  obtained?     (c)  How  does  the  measuring  point  of 
the  mechanical   drawing  pencil  differ  from  the  point  of  the 
sketching  pencil  ? 

22.  What  are  the  uses  of  a  scale  in  laying  out  a  drawing  ? 

23.  Show  by  a  sketch  how  to  lay  off  a  distance  of  16' -3£", 
using  the  architect's  scale  \"  to  I'-O". 

24.  How  are  the  legs  of  the  compass  set  for  describing  circles  ? 

25.  (a)  What  is  the  shape  of  the  point  of  the  lead  used  in 
the  bow  compass?     (b)  How  should  it  be  set  with  reference  to 
the  needle  point  ? 

26.  (a)  What  is  the  range  of  the  bow  compass?     (b)  How 


156  MECHANICAL  DRAWING 

are  the  circles  drawn  which   are  too  large  for  the  ordinary 
compass  ? 

27.  Show  by  a  sketch  how  to  divide  a  line  into  five  equal  parts 
by  means  of  the  dividers. 

28.  Illustrate  by  a  sketch  and  show  calculations  for  deter- 
mining the  size  of  an  enclosing  rectangle. 

29.  Describe  the  process  of  drawing  the  border  rectangle  for 
a  mechanical  drawing  sheet. 

30.  (a)  Define  the  constructive  stage  of  the  mechanical  draw- 
ing,   (b)  How  are  hidden  edges  shown  in  this  stage  ? 

31.  In  what  order  are  the  lines  drawn  in  the  finishing  stage  ? 

32.  (a)  What  space  is  left  between  the  outline  of  the  object 
and  the  end  of  the  extension  line?     (b)   How  far  should  the 
extension  line  run  beyond  the  arrowhead?     (c)  How  far  should 
the  nearest  dimension  line  be  from  the  outline  of  the  object? 
(d)  How  far  apart  should  dimension  lines  be  placed? 

33.  (a)  What  is  the  height  of  the  whole  number  in  a  dimen- 
sion?   (b)   The  total  height  of  the  fraction? 

34.  What  is  the  purpose  of  notes  on  a  drawing  ? 

35.  What  is  the  title  block? 

36.  Describe  the  steps  taken  in  balancing  two  or  more  lines 
in  a  title. 

37.  What  dimension  forms  are  used  in  showing  the  inclination 
of  a  line  ? 

38.  In  what  order  are  the  lines  drawn  when  an  arc  and  a 
straight  line  are  tangent  to  each  other? 

39.  (a)   Show  two  ways  of  dimensioning  a  radius,     (b)  Under 
what  condition  is  each  used? 

DATA  FOE  REVIEW  PROBLEMS 

Given:     A  perspective  sketch,  Fig.  163. 
Required: 

1.  To  make  an  orthographic  sketch  of  the  object  shown  in 
Fig.  163. 

2.  To  make  a  pencil  mechanical  drawing  from  the  ortho- 
graphic sketch. 

Given:     A  perspective  sketch,  Fig.  164. 


PENCIL  MECHANICAL  DRAWING 


157 


Required: 

1.  To  make  an  orthographic  sketch  of  the  object  shown  in 
Fig.  164. 

2.  To  make  a  pencil  mechanical  drawing  from  the  ortho- 
graphic sketch 

Given:    A  perspective  sketch,  Fig.  165. 
Required : 

1.  To  make  an  orthographic  sketch  of  the  object  shown  in 
Fig.  165. 


FIG.  163.    KEYED  MORTISE  AND  TENON 


2.  To  make  a  pencil  mechanical  drawing  from  the  ortho- 
graphic sketch. 


158 


MECHANICAL  DRAWING 


FIG.  164.    FOOT  STOOL 


FIG.  165.    DASH  POT  ARM 


CHAPTER  IV 

TRACING  AND  BLUEPRINTING 

PROSPECTUS 

The  pencil  mechanical  drawing  of  Chapter  III  is  continued 
in  this  chapter  to  develop  further  skill  in  the  use  of  instruments 
and  to  improve  the  technique  in  both  the  mechanical  and  free- 
hand elements  of  the  drawing.  It  is  the  chief  aim  of  this  chap- 


r 


FIG.  166.     TYPE  PROBLEM.    DRAWING  BOARD 


ter  to  familiarize  the  student  with  the  instruments,  materials, 
and  methods  used  in  inking  and  to  fix  a  standard  for  the  ink 
drawing.  As  a  result  of  the  work  of  this  chapter  the  student 
should  be  able  to  make  neat  tracings  with  proper  width  of  lines, 
good  joints,  and  uniform  spacing  in  crosshatching.  The  tech- 
nique of  the  lettering,  arrowheads,  and  figures  should  be  com- 
parable with  that  secured  in  the  mechanical  line  work. 

159 


TRACING  AND  BLUEPRINTING 


161 


The  tracing  of  the  pencil  mechanical  drawing  on  tracing  cloth 
with  ink  is  usually  the  last  step  in  the  production  of  a  drawing 
for  the  shop  or  for  other  purposes  where  a  number  of  copies  of 
the  drawing  are  desired.  The  tracing  is  made  on  a  transparent 
cloth  or  paper  in  order  that  the  blueprints  may  be  made  from  it 
as  described  later.  The  use  of  the  blueprint  makes  it  possible  te 
have  several  copies  of  the  drawing  and  at  the  same  time  preserve 
the  original  tracing  from  which  other  copies  may  be  made  at 
any  time. 


,_ 

ZJy      M«V^M~  ^(^••••^•M.k.^i 

J36  33 


A 

1 
1 

3 

X 

Zl 

??. 

15           ' 

!        n 

16 

13 

FIG.  168.    EEVIEW  PROBLEM 


PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  18 

Inasmuch  as  the  drawings  of  many  objects  require  the  use  of 
sections,  the  student  should  review  both  the  half  and  the  quarter 
sections  discussed  in  Chapter  III,  pages  98  and  99,  and  test 
his  knowledge  of  the  orthographic  principles  involved  in  making 
sectional  views  by  answering  the  following  questions.  See  Figs. 
99  and  168. 


162 


MECHANICAL-DRAWING 


1.  Where  is  the  surface  1,  6,  shown  in  the  side  view  ? 

2.  (a)  Does  the  rectangle  20,  21,  22,  23  in  the  side  view 
represent  an  opening  or  a  solid  part  of  the  object?     (b)  Why? 

3.  Where  is  the  surface  7,  4  shown  in  the  side  and  top  views  ? 

4.  Make  a  front  view  of  the  object  when  cut  on  A  B. 

5.  (a).  Is  the  side  view  affected  by  the  section?     (b)   Top 
view? 


FIG.  169.    INSTRUMENT  CASE 

Bach  tracing  in  this  chapter  will  be  preceded  by  a  pencil 
mechanical  drawing.  The  pencil  drawing  is  made  to  give  the 
student  additional  practice  in  the  handling  of  the  instruments 
already  used,  to  introduce  the  use  of  new  instruments,  and  to 
provide  drawings  for  the  tracings. 


DATA  FOR  DRAWING  PLATE  18 

Given:     Orthographic  drawings,  Figs.  169,  170,  171. 

Required:  To  make  a  pencil  mechanical  drawing  of  thei 
object  shown  in  Fig.  169,  170,  or  171  as  assigned  by  the  in- 
structor. The  views  given  and  required  may  be  obtained  from 
the  following  statements.  Any  similar  problems  may  be  substi- 
tuted by  the  instructor. 


TRACING  AND  BLUEPRINTING 


163 


Given :     Fig.  169.     The  front,  top,  and  right  side  views. 
Required:     To  draw  the  front,  top,  and  left  side  half  section 


views. 


FIG.  170.    MEDICINE  CABINET 


Given:    Fig.  170.    The  front  and  right  side  views. 
Required:     To  draw  the  front  and  left  side  half  section 
views.  • 

Given:    Fig.  171.    The  front  and  right  side  views. 
Required:     To  draw  the  front,  and  left  side  half  section. 

Instructions: 

Proceed  as  for  the  mechanical  drawing  plates  of  Chapter  III. 


164 


MECHANICAL  DRAWING 


DATA  FOR  LETTERING  PLATE  18 

Given:    Plate  18  to  reduced  size.    Fig.  172. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


Tow 

Bur/ap?  — 
Laced  Webb/, 


$ecf/on  showing  construction 
of  cushion 

FIG.  171.    FOOT  STOOL 


PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE   19 

The  following  is  a  list  of  the  instruments  and  materials  needed 
to  make  tracings  and  reproductions  of  mechanical  drawings : 

1.  Tracing  cloth. 

2.  Tracing  paper. 

3.  Blueprint  paper. 

4.  Black  waterproof  ink. 

5.  Ruling  pen. 

6.  Compass. 

7.  Bow  pen. 


TRACING  AND  BLUEPRINTING  165 

Tracing  Cloth  is  a  thin,  firm  cloth  sized  to  hold  ink  and  to 
make  the  cloth  transparent.  It  is  generally  used  when  drawings 
are  to  be  reproduced  by  the  blue,  black,  or  brown  printing  proc- 
ess. Drawings  made  on  tracing  cloth  may  be  kept  indefinitely 
if  the  cloth  is  kept  dry  and  handled  carefully.  Changes  may  be1 
made  on  the  drawings  and  new  prints  made  from  time  to  time. 


zBORE  2"  ON  ALL  FUTURE  z 
zORDERS  BOTH  NEW  AND  z 
=  REPAIR  IRRESPECTIVE  OFz 
zWHAT  ORIGINAL  ORDER  z 
z  CALLS  FOR  STANDARD  WASHER? 


FIG.  172.    LETTERING  PLATE  18 

One  side  of  the  cloth  is  glazed  and  the  other  is  dull.-  Either 
side  may  be  used  for  inking.  The  glazed  side  will  admit  of  the 
.most  erasing,  but  when  inking  is  done  on  this  side  the  cloth  will 
curl.  For  work  where  penciling  is  to  be  done  on  the  cloth,  for 
drawings  to  be  used  for  photographic  reproduction,  and  for 
tinting,  the  dull  side  should  be  used.  For  the  tracings  of  this 
chapter  use  the  dull  side. 

Sometimes  the  ink  does  not  adhere  readily  to  the  surface  of 
the  cloth,  particularly  when  the  glazed  side  is  used.  To  over- 
come this  difficulty  powdered  chalk  may  be  rubbed  into  the  sur- 
face with  a  soft  cloth.  The  chalk  should  be  thoroughly  removed 
before  beginning  inking. 

The  cloth  is  fastened  to  the  board  with  the  same  thumb  tacks 
used  to  hold  the  pencil  drawing.  In  order  to  avoid  shifting  this 


166 


MECHANICAL  DRAWING 


drawing,  the  cloth  should  be  spread  over  the  sheet  and  one  tack 
at  a  time  removed  and  inserted  through  the  cloth  into  the  hole 
from  which  it  came. 

Tracing  Paper.  For  temporary  drawings,  especially  where 
some  portion  of  a  drawing  already  made  can  be  traced  and  used 
as  part  of  a  new  drawing,  a  thin,  transparent  paper  called 
tracing  paper  may  be  used  with  considerable  saving  of  time.  It 
should  not  be  used  for  a  permanent  drawing  or  one  which  requires 
much  handling. 


FIG.  173.    BLUEPRINTING  FRAME 


Blueprint  Paper.  Instead  of  sending  the  tracing  into  the 
shop  where  it  would  soon  be  injured  or  worn  out,  prints  are 
made,  usually  on  blueprint  paper.  This  is  a  white  paper  covered 
with  a  solution  which  after  being  exposed  to  light,  turns  blue. 

The  Blueprinting  Process.  To  make  prints,  the  inked  side  of 
the  tracing  is  placed  against  the  glass  of  a  printing  frame.  The 
sensitized  side  of  the  blueprint  paper  is  then  placed  against  the 
tracing  cloth  and  held  firmly  in  contact  with  it.  The  contact  is 
secured  by  means  of  clamps  attached  to  the  back  of  the  board 
of  the  printing  frame  which  holds  both  the  tracing  and  the  blue- 
print paper  in  place.  Fig.  173. 

The  printing  frame  should  be  placed  in  a  direct  light.  If 
sunlight  is  used  the  exposure  should  be  made  during  the  middle 
of  the  day.  The  length  of  exposure  to  the  light  depends  on  the 
intensity  of  the  sunlight  or  plpntrie  light  and  upon  the  " speed" 


TRACING  AND  BLUEPRINTING  167 

of  the  blueprint  paper.  After  removing  the  paper  from  the 
frame  it  should  be  washed  by  turning  it  over  several  times  in  a 
basin  of  water.  This  removes  the  chemical  on  the  sensitized  side 
of  the  paper  which  was  covered  by  the  lines  of  the  drawing  on 
the  tracing  cloth  and  leaves  the  white  paper  exposed,  forming 
the  outline  of  the  blueprint  drawing.  The  result  is  a  reproduc- 
tion of  the  drawing  in  white  lines  with  a  blue  background.  After 
the  blueprint  has  been  washed  it  should  be  hung  vertically  by  one 
edge  or  over  a  horizontal  stick  to  drain,  and  allowed  to  remain 
until  it  is  dry. 

Black  Ink  will  be  used  for  all  lines  on  the  plates  of  this  chap- 
ter. Black  drawing  ink  is  composed  of  finely  divided  carbon 
held  in  suspension  in  a  liquid.  When  a  line  is  drawn  with  this 
ink  the  liquid  dries  and  leaves  the  carbon  deposited  on  the  paper 
or  cloth.  It  is  important  that  enough  ink  be  left  on  the  line  so 
that  when  the  ink  is  dry  the  amount  of  carbon  deposited  will  be 
sufficient  to  make  the  line  black.  Thin  ink  gives  brown  lines. 
The  liquid  used  in  drawing  ink  evaporates  quickly.  The  carbon 
therefore  dries  quickly,  permitting  one  to  work  rapidly  while 
tracing.  The  rapid  evaporation  of  the  ink  necessitates  keeping 
the  stopper  always  in  the  bottle  to  prevent  the  ink  from  becoming 
too  thick. 

The  Ruling  Pen  is  used  more  than  any  other  instrument  in  the 
draftsman's  outfit  and  should  therefore  be  carefully  selected. 
The  steel  of  which  the  pen  is  made  should  be  properly  tempered 
and  of  such  quality  as  to  retain  a  smooth  sharp  edge.  The  blades 
should  be  of  the  same  length,  the  inner  one  sufficiently  stiff  to 
resist  a  light  pressure  against  the  ruling  edge.  The  nibs  should 
be  of  the  same  width,  equally  rounded  and  directly  opposite  one 
another.  The  ends  of  the  nibs  should  be  narrow  enough  to  give 
control  in  starting  and  ending  lines,  but  broad  enough  to  hold 
a  reasonable  amount  of  ink.  When  the  nibs  are  too  narrow  the 
ink  is  drawn  from  the  points  by  capillary  attraction,  making  it 
difficult  to  start  the  ink  at  the  beginning  of  a  line. 

Filling  and  Using  the  Pen.  The  ruling  pen  should  be  ad- 
justed, filled,  and  used  in  the  following  manner : 

1.  Adjust  the  pen  by  turning  the  thumb  screw  to  approxi- 
mately the  proper  width  of  line. 


168 


MECHANICAL  DRAWING 


2.  Fill  the  pen  by  inserting  the  quill,  attached  to  the  stopper 
of  the  ink  bottle,  between  the  nibs  of  the  pen.    The  pen  should 
be  filled  to  a  height  of  about  \" .    Care  should  be  taken  to  avoid 
getting  ink  on  the  outside  surfaces  of  the  nibs. 

3.  Set  the  pen  to  give  the  exact  width  of  line  required,  testing 
it  on  the  margin  of  the  drawing  or  on  a  separate  sheet.    It  should 
be  tested  on  the  same  kind  of  surface  as  that  on  which  it  is  to  be 
used  and  by  ruling  along  a  straightedge — not  freehand. 


FIG.  174.    EULING  A  HORIZONTAL  LINE 


4.  Hold  the  pen  in  the  hand,  as  shown  in  Fig.  174,  with  the 
first  finger  above  the  thumb  screw  and  the  second  finger  against 
the  right  side  of  the  pen.    It  should  be  held  in  a  vertical  plane, 
but  may  be  allowed  to  lean  slightly  in  the  direction  of  motion. 
In  this  position  both  nibs  will  touch  the  cloth  with  equal  pressure, 
which  is  essential  to  the  production  of  smooth,  sharply  defined 
lines. 

5.  Draw  rather  slowly  with  a  movement  of  the  hand  and  arm, 
the  forearm  remaining  perpendicular  to  the  line  being  drawn. 
There  should  be  no  wrist  movement,  as  the  pen  must  not  be 
rotated  upon  its  axis.     The  tips  of  the  third  and  fourth  fingers 
should  slide  on  the  surface  of  the  T-square  or  triangle  to  steady 
the  hand.    As  the  end  of  the  line  is  approached  the  motion  of 
the  hand  and  arm  should  cease  and  the  line  should  be  completed 
with  a  finger  movement.    The  center  of  the  ink  line  on  the  tracing 
should  be  directly  over  the  pencil  line  on  the  drawing  being 


TRACING  AND  BLUEPRINTING  169 

traced.  Care  must  be  taken  to  set  the  pen  exactly  at  the  begin- 
ning of  a  line.  At  the  end  of  a  line  the  pen  should  be  lifted 
vertically  in  order  that  the  ink  will  not  run  out  and  cause  the 
line  to  overrun.  In  drawing  dotted  lines,  the  pen  must  be  set 
down  vertically,  the  dash  drawn,  and  the  pen  then  lifted  ver- 
tically so  as  to  make  both  ends  of  the  dash  square. 

The  spacing  of  section  lines  is  done  entirely  by  eye.  In  order 
to  avoid  varying  the  spaces  the  pen  should  be  placed  against  the 
ruling  edge  and  the  perpendicular  distance  from  the  point  of 
the  pen  to  the  last  line  drawn  made  equal  to  the  perpendicular 
distance  between  any  two  sequential  preceding  lines. 

When  starting  the  crosshatching  in  a  corner,  there  is  a  ten- 
dency to  space  the  lines  too  closely,  the  spaces  increasing  as  the 
lines  become  longer.  The  student  should  practice  crosshatching 
rectangular  areas  on  a  scrap  of  tracing  cloth  before  attempting  to 
work  on  the  drawing. 

Cleaning  the  Pen.  The  pen  should  be  cleaned  frequently  by 
inserting  a  cloth  at  the  side  and  pulling  it  out  between  the  nibs. 
This  should  be  done  frequently  while  the  pen  is  in  use.  The  pen 
should  not  be  laid  away  until  the  surfaces  are  thoroughly  cleaned, 
as  ink  will  corrode  steel.  If  the  ink  does  not  start  readily  at  the 
beginning  of  a  line,  squeeze  the  nibs  of  the  pen  together  slightly 
to  draw  the  ink  down  to  the  point.  If  the  ink  has  been  allowed 
to  stand  for  some  time,  the  pen  should  be  cleaned  and  refilled. 
Do  not  touch  the  pen  to  the  hand  or  a  cloth  to  start  the  ink. 

Sharpening  the  Pen.  The  nibs  of  the  pen  should  be  as  sharp 
as  they  can  be  made  without  producing  the  sensation  of  cutting 
when  the  pen  is  in  use.  They  should  not  scratch  the  paper  when 
drawing  a  line.  This  occurs  if  they  are  sharpened  to  a  point 
instead  of  a  rounded  edge,  or  if  the  point  is  rough  or  notched. 
The  length  and  condition  of  the  points  may  be  tested  by  holding 
the  pen  up  to  the  light  and  bringing  the  nibs  together  slowly. 

In  case  the  pen  becomes  broken  or  dull  from  use  it  should  be 
sharpened  as  follows : 

1.  Provide  a  close  grained  oilstone. 

2.  Close  the  nibs  until  they  just  touch  each  other. 

3.  Hold  the  pen  on  the  stone  as  in  drawing  a  line  and  move 
it  back  and  forth,  revolving  it  slowly  in  the  plane  of  motion  until 


170 


MECHANICAL  DRAWING 


the  nibs  are  evenly  rounded  and  of  the  same  length.    Fig.  175. 
This  will  dull  the  nibs. 

4.  Separate  the  nibs  and  sharpen  them  by  rubbing  the  outside 
on  the  oilstone,  giving  at  the  same  time  a  slight  rotary  motion 


FIG.  175.     SHARPENING  THE  PEN.    EVENING  THE  NIBS 


FIG.  176.     SHARPENING  THE  PEN.     GRINDING  THE  NIBS 

to  the  handle,  which  is  held  at  a  small  angle  with  the  face  of  the 
stone.  Fig.  176.  The  point  of  the  pen  should  be  examined  fre- 
quently and  the  process  continued  until  the  nibs  are  sharp.  If 
a  burr  is  produced  on  the  inside  of  a  nib  it  may  be  removed  by 
placing  the  inside  surface  flat  against  the  oilstone  and  rubbing 
it  lightly. 

The  Compass.     When  using  the  compass  for  either  penciling 
or  inking,  the  legs  should  be  adjusted  so  that  the  pen  or  pencil 


TRACING  AND  BLUEPRINTING  171 

part  and  the  needle  point  are  perpendicular  to  the  drawing 
board.  With  the  legs  in  this  position,  the  compass  revolves  about 
the  needle  point  as  an  axis  and  the  two  nibs  of  the  pen  bear 
with  equal  pressure,  thus  producing  sharply  defined  Jines.  The 
compass  is  held  by  the  handle,  between  the  thumb  and  first  finger 
of  the  right  hand.  It  is  rotated  by  rolling  the  handle  between 
the  thumb  and  finger.  Fig.  177.  If  the  compass  is  allowed  to 
lean  very  slightly  in  the  direction  of  motion,  sufficient  pressure 
may  be  put  on  the  pen  or  pencil  to  hold  it  firmly  in  contact  with 
the  paper  or  cloth  without  danger  of  the  needle  point  being  lifted 
from  the  center. 


FIG.  177.    DRAWING  A  CIRCLE  WITH  THE  COMPASS 

The  pen  of  the  compass  is  filled,  adjusted,  cleaned,  and  sharp- 
ened in  the  same  manner  as  the  ruling  pen. 

The  Bow  Pen  should  be  used  for  all  circles  and  arcs  of  f  " 
radius  or  less.  The  pen  should  be  filled  and  adjusted  in  the  same 
manner  as  the  ruling  pen. 

Line  Notation.  In  inking,  the  object  lines  are  drawn  notice- 
ably heavier  than  all  other  lines  except  the  border  line.  The  dif- 
ference in  width  produces  a  sharp  contrast  between  classes  of 
lines  which  makes  the  drawing  easy  to  read  and  gives  it  a  good 
appearance.  In  small  drawings  or  those  containing  intricate 
detail  the  width  of  the  object  lines  is  slightly  reduced. 

No  system  of  line  notation  has  ever  been  universally  adopted. 
In  this  course  a  simple  one  conforming  to  average  commercial 
drafting  room  practice  will  be  used.  All  lines  except  the  dotted 
line  used  to  represent  invisible  edges  are  solid.  The  widths  of 


172  MECHANICAL  DRAWING 

lines  to  be  used  in  this  course  are  given  in  Fig.  178.  All  widths 
as  indicated  in  Fig.  178  should  be  estimated  by  the  student.  As 
far  as  possible  all  lines  of  the  same  width  should  be  drawn  while 
the  pen  is  set  for  that  width.  Before  starting  to  ink  a  group  of 
lines  of  the  same  width  a  sample  line  should  be  drawn  on  the  edge 
of  the  sheet.  This  may  be  used  as  a  guide  in  setting  another 
instrument  to  give  the  same  width  of  line.  For  instance,  when 
the  compass  is  used  in  drawing  circles  a  sample  of  the  width  of 
line  should  be  drawn  to  aid  in  estimating  the  setting  of  the  ruling 
pen  which  will  be  used  later.  In  case  the  pen  must  be  reset  for 
a  particular  line  the  estimated  width  should  be  determined  by 
drawing  lines  near  the  sample  until  the  proper  width  of  line 
is  secured. 

CENTEELINE  ..........  *] 

EXTENSION  LINE  ......  I    t  „  WTT,..-,  _ 

DIMENSION  LINE  ......  P"»    W1LUJJ 

CEOSSHATCHING  LINE. 


FULL          -&'  WIDE 
DOTTED     - 


T  r\nrQ 
'S 


BORDER  LINE  ............  .  -&'  WID 


FIG.  178.    LINE  NOTATION  FOR  INK  DRAWINGS 

Order  of  Inking  the  Drawing.     The  drawing  should  be  inked 
in  the  order  given  below  to  secure  economy  of  time  and  effort. 

1.  Object  lines. 

a.  Circles  and  arcs  of  circles. 

b.  Horizontal  lines  (beginning  at  the  top). 

c.  Vertical  lines  (beginning  at  the  left). 

d.  Inclined  lines. 

2.  Center  lines  (same  order  as  object  lines). 

3.  Extension  and  dimension  lines  (same  order  as  object  lines). 

4.  Arrowheads. 

5.  Dimension  figures  and  notes. 

6.  "Crosshatching  lines. 

7.  Title. 

8.  Border  line. 

In  inking  the  title  and  notes,  pencil  guide  lines  on  the  tracing 


TRACING  AND  BLUEPRINTING  173 

cloth  will  be  found  of  great  assistance  in  keeping  the  letters 
uniform  in  height.  In  no  case  should  letters  and  figures  be 
penciled  on  the  tracing  cloth  over  those  which  appear  on  the 
pencil  drawing,  before  they  are  inked.  The  pencil  drawing 
should  serve  as  a  copy  for  inking  figures,  letters,  and  arrowheads 
as  it  does  for  all  mechanical  lines.  All  freehand  inking  should 
be  done  with  the  writing  pen  as  described  under,  "Preparatory 
Instruction  for  Lettering  Plate  11,"  page  102. 

Erasure.  On  ink  drawings  erasures  must  be  carefully  made, 
especially  if  inking  is  to  be  done  over  the  erased  areas.  It  will 
be  found  that  if  the  ruby  eraser  is  used  for  removing  ink  lines 
the  drawing  surface  will  be  left  in  good  condition  for  re-inking. 
In  case  a  blot  occurs  the  ink  should  not  be  allowed  to  soak  into 
the  tracing  cloth.  As  much  of  the  ink  as  possible  should  be. 
taken  up  with  a  blotter  or  cloth  and  the  remainder  allowed  to  dry 
before  erasing.  The  erasing  shield  should  be  used  to  protect  the 
parts  of  the  drawing  which  are  not  to  be  erased,  as  described  on 
page  132. 

Trimming  the  Tracing  Cloth.  When  the  tracing  is  finished 
lay  off  one-half  an  inch  from  each  corner  of  the  border  rectangle 
to  make  a  one-half  inch  margin.  Place  the  tracing  on  the  back 
of  the  drawing  board.  With  a  'sharp  knife  running  along  the 
edge  of  the  T-square  blade  not  used  for  ruling,  trim  the  sheet  to 
the  rectangle  determined  by  the  eight  pencil  points.  In  this 
process  the  T-square  blade  should  be  placed  over  the  finished 
portion  of  the  sheet.  The  drawing  will  then  be  held  firmly  and 
will  be  protected  from  the  knife  in  case  it  should  slip. 

DATA  FOB  DRAWING  PLATE  19 

Given:     The  pencil  mechanical  drawing,  Plate  18. 
Required:    To  make  a  tracing  of  Plate  18. 

Instructions: 

1.  Fasten  the  tracing  cloth  over  the  mechanical  drawing  and 
prepare  the  surface  for  inking  as  previously  described  under, 
"Tracing  Cloth,"  page  165. 

2.  Ink  the  drawing,    following    the    steps   outlined    under, 

of  Inking  the  Drawing,"  page  172. 


174  MECHANICAL  DRAWING 

DATA  FOB  LETTERING  PLATE  19 

Given:     Plate  19  to  reduced  size.    Fig.  179. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


:END    OF   STUD   TO  BE   FLAT€ 
TENED   AND  CAST   IN  -PARTz 

:  USE   FILLERS    513   TO-  ALLOW  GEARS   TOZ 
'MESH    PROPERLY.     CROSS   HEAD   PIN  ASZ 

SHOWN       CROSS    HEAD   PIN 


FIG.  179.    LETTERING  PLATE  19 


DATA  FOR  DRAWING  PLATE  20 

Given:     Orthographic  drawings,  Figs.  182,  183,  184, and  185. 

Required:  To  make  a  pencil  mechanical  drawing  of  the 
object  shown  in  Fig.  182,  183,  184,  or  185,  as  assigned  by  the 
instructor.  The  views  given  and  required  may  be  obtained  from 
the  following  statements.  Any  similar  problem  may  be  substi- 
tuted by  the  instructor. 

Given:     Fig.  182.    The  front  and  left  side  views. 

Required:     To  draw  the  front  and  right  side  views. 

Given:     Fig.  183.    The  front  and  left  side  views. 

Required :     To  draw  the  front  and  right  side  views. 

Given:     Fig.  184.    The  front  and  left  side  views. 

Required:     To  draw  the  front  and  right  side  views. 

Given:     Fig.  185.    The  front  and  left  side  views. 

Required :     To  draw  the  front  and  right  side  views. 


WER  GIRTH    3-eX.g" 


SILL  2- 

= 

CONCHETE      FOUNDATION 


FIG.  180.     TYPE  PROBLEM.     BARN  FRAMING.     GIVEN  VIEWS 


FIG.  181.    TYPE  PROBLEM.    BARN  FRAMING.    I'INISHFD  DRAWING 

(175) 


176 


MECHANICAL  DRAWING 


Bere/ 


13 


fo  coyer 

FIG.    182.     CAMP   STOOL 


FIG.  183.    STEP  LADDER 


TRACING  AND  BLUEPRINTING 


177 


y  A 


5-0" 

Al/wa//s  Z±  fh/ck 

FIG.  184.    FORMS  FOR  CONCRETE  DOG  KENNEL 


•r 
1 

f 

.1. 

'T' 

1 

t 

/' 

gg 

3 

65r™~  - 

4J 

( 

~ 

•*  

-2 

?' 

f-o0  >. 
-3*  

•f 

—  ^ 

FIG.  185.    SAW  BUCK 


178  MECHANICAL  DRAWING 


DATA  FOB  LETTERING  PLATE  20 

Given:     Plate  20  to  reduced  size.    Fig.  186. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


Z2'-l|"xl9f    ROUGH    ROUND   RODS  ~  DRILL    Z 

=  I4-24JFLAT_HEAD_SCREW= 

Zf-ll    BOLTS -6g"   LONG    WITH    NUT   AND    Z 
ZCHECK^NUT       |"-I6    ROUND   HEAD   BOLTZ 

zCONNECTING   ROD  BEARINGz 


FIG.  186.     LETTERING  PLATE  20 


DATA  FOE  DRAWING  PLATE  21 

Given:     The  pencil  mechanical  drawing,  Plate  20. 
Required:     To  make  a  tracing  of  Plate  20. 

Instructions: 

1.  Fasten  the  tracing  cloth  over  the  mechanical  drawing  and 
prepare  the  surface  for  inking. 

2.  Ink   the    drawing,    following    the    steps    outlined    under 
"Order  of  Inking  the  Drawing,"  page  172. 

3.  Trim  the  sheet  and  press  the  cloth  back  into  the  tack  holes. 


TRACING  AND  BLUEPRINTING  179 

DATA  FOR  LETTERING  PLATE  21 

Given:     Plate  21  to  reduced  size.    Fig.  187. 
Required:    To  make  the  plate  to  an  enlarged  scale. 


2    FILLER    PLATES"  -5x9'x2-4'/         REAM! 
2    PIN    PLATES    INSIDE    {xHx2'-6*       JIG! 


2    HINGE    PLATES    OUTSIDE    ^xlO"x2" 
LATERAL   PLATE  .  |x  20Bxr-o|*  ALL 

HOLES    £       COUNTERSUNK    g         RIVETS 
FIG.  187.     LETTERING  PLATE  21 


FIG.  188.     TYPE  PROBLEM.     RESERVOIR  CAP.     GIVEN  VIEWS 


PEEPABATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  22 


Q_ 

5 


ir 

LJ 

(ft 

LU 

or 


TRACING  AND  BLUEPRINTING 


181 


DATA  FOR  DRAWING  PLATE  22 

Given:    Orthographic  drawings,  Figs.  190, 191, 192, and  193. 

Required:  To  draw  the  views  of  the  object  shown  in  Fig. 
190,  191,  192,  or  193,  as  assigned  by  the  instructor,  from  the 
following  statements.  Any  similar  problem  may  be  substituted 
by  the  instructor. 


FIG.  190.    BOOK  BACK 


Given:     Fig.  190.    The  front  and  right  side  views. 
Required:     To  draw  the  front  and  left  side  views. 

Given:    Fig.  191.    The  front  and  left  side  views. 
Required:     To  draw  the  front  half  section  and  right  side 
views. 

Given:    Fig.  192.    The  front  and  left  side  views. 
Required:     To  draw  the  frjont  half  section  and  right  side 
views. 

Given:     Fig.  193.    The  front  and  left  side  views. 
Required:     The  front  half  section  and  left  side  views. 


182 


MECHANICAL  DRAWING 


FIG.  191.     COUNTER  SHAFT  PULLEY  FOR  12"  WOOD  LATHE 


— •hr1 
? 


K 


U*- 


FIG.  192.    HAND  WHEEL  FOR  12"  WCOD  LATHE 


DATA  FOR  LETTERING  PLATS  22 

Given:     Plate  22  to  reduced  size.    Fig.  194. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


FIG.  193.    LEG  FOR  12"  WOOD  LATHE 


4  CHANNELS.  I2'xl4'-8f"  ROOF  TRUSSZ 
I  COAT  OF_  GRAPHITE  PAINT  DRILL  Jz 
12  HOLES  EQUALLY  SPACED  TO  FIT  Z 

PIECE  NO,  ii7  PISTON  FOR  10  z 
HP,  HORIZONTAL  ENGINE  z 


FIG.  194.    LETTERING  PLATE  22 


(183) 


184  MECHANICAL  DRAWING 


I^EPARATORY  INSTRUCTION  FOR  DRAWING  PLATE  23 

•  Locating  Points  of  Tangency.  To  secure  perfect  joints  where 
lines  are  tangent  in  the  tracings,  the  exact  points  of  tangency 
should  be  located  and  marked  in  pencil  on  the  tracing  cloth. 
The  method  of  locating  the  tangent  points  depends  upon  the  geo- 


FIQ.  195.    METHOD  OF  LOCATING  POINTS  OF  TANGENCY 

metrical  principle  that  a  line  perpendicular  to  a  tangent  at  its 
point  of  contact  passes  through  the  center  of  the  circle. 

To  locate  a  point  of  tangency,  place  the  hypotenuse  of  eitheb 
triangle  against  any  edge  of  the  other  triangle,  as  shown  in 
Fig.  195.  Move  both  triangles  as  one  tool  until  a  side  of  the 
triangle  A  is  coincident  with  the  tangent  line.  "With  triangle  B 
held  firmly  in  place,  slide  triangle  A  into  the  position  marked 
A'  where  the  side  at  right  angles  to  the  tangent  line  passes 
through  the  center  of  the  arc.  A  short  dash  should  be  drawn 
across  the  tangent  line  to  mark  the  point  of  tangency. 

The  point  of  tangency  between  two  arcs  may  be  located  by 
drawing  the  straight  line  joining  their  centers.  This  line  passes 
through  their  point  of  contact.  Fig.  195. 


TRACING  AND  BLUEPRINTING  185 


DATA  FOR  DRAWING  PLATE  23 

Given:     The  pencil  mechanical  drawing,  Plate  22. 
Required:     To  make  a  tracing  from  Plate  22. 

Instructions: 

1.  Fasten  the  tracing  cloth  and  prepare  it  for  inking. 

2.  Locate  the  points  of  tangency. 


3. 


Locate  the  points  of  tangency. 

Ink  the  drawing  in  the  usual  order. 

Trim  the  sheet  and  press  the  cloth  back  into  the  tack  holes. 


A   DRAWING/ THE"  MECHANICAL PART  Z 

> 

OF    WHICHJS    WELL    EXECUTED     MAY    Z 

I 

HAVE  ITS~APPEARANCE  SPOILED  BY  Z 
POOR  LETTERING  MAKE  THE  LAST  Z 
PLATE  THE  BEST  OF  ALL"~I  2  34  5  61. 


FIG.  196.    LETTERING  PLATE  23 


DATA  FOR  LETTERING  PLATE  23 

Given:    Plate  23  to  reduced  size.    Fig.  196. 
Required :     To  make  the  plate  to  an  enlarged  scale. 


KEVIEW  QUESTIONS 

1.  (a)  What  is  the  difference  between  the  two  sides  of  the 
tracing  cloth?     (b)  Which  side  is  used  in  this  course? 


186 


MECHANICAL  DRAWING 


2.  (a)  Describe  the  process  of  fastening  the  cloth  over  the 
pencil  drawing,     (b)  How  is  the  cloth  prepared  for  inking? 

3.  Describe  the  process  of  making  a  blueprint  from  a  tracing. 


"  -—  . 

& 

r 

£ 

>* 

^S-f* 

4  j 

FIG.   197.    GOVERNOR  SUPPORT 

4.  (a)   How  is  the  ruling  pen  held  for  ruling  lines  ?    (b)  How 
is  it  adjusted  to  the  proper  width  of  line?     (c)  How  is  it  filled? 
(d)  How  cleaned? 

5.  (a)  "What  precautions  are  taken  in  beginning  and  ending 
a  line?     (b)  How  does  the  pen  approach  and  leave  the  paper 
in  drawing  dotted  lines? 

6.  How  are  the  spaces  between  crosshatching  lines  estimated  ? 

7.  (a)  Why  are  the  needle  point  and  the  pen  and  pencil 
points  of  the  compass  set  at  right  angles  to  the  plane  of  the 
drawing  paper?     (b).How  is  the  compass  held  when  drawing  a 
circle?     (c)  How  is  it  rotated? 


TRACING  AND  BLUEPRINTING 


187 


8.  (a)   In  inking,  why  are  the  object  lines  made  wider  than 
the  other  lines?     (b)  Give  the  standard  width  of  inked  object, 
extension,  dimension,  and  center  lines,  and  the  border  line. 

9.  In  what  order  are  the  different  kinds  of  lines  inked? 


FIG.  198.    PLANING  JIG  FOR  ROD  BRASSES 


10.  (a)  In  what  order  are  the  object  lines  inked?     (b)  Cen- 
ter lines?     (c)  Extension  and  dimension  lines? 

11.  How  is  ink  removed  from  a  drawing  ? 

12.  How  is  the  tracing  trimmed  to  the  required  size  ? 

13.  (a)  Upon  what  geometrical  principle  does  the  method  of 
finding  the  point  of  tangency  between  an  arc  and  a  straight  line 
depend?     (b)   Give  the  steps  in  the  construction  necessary  to 
locate  a  point  of  tangeuoy. 


188 


MECHANICAL  DRAWING 


DATA  FOB  REVIEW  PROBLEMS 

Given:  The  top,  front,  and  right  side  views  of  an  object, 
Fig.  197. 

Required:  To  draw  the  top,  front  half  section,  and  right 
side  views  of  the  object  shown  in  Fig.  197.  Scale,  full  size. 

Given:  The  top,  front,  and  right  side  views  of  an  object. 
Pig.  198. 

Required:  To  draw  the  top,  front,  and  left  side  views  of 
the  object  shown  in  Fig.  198.  Scale,  half  size. 


DRILL  T" 


FIG.  199.    STUFFING  Box  GLAND 


Given:     The  top  and  right  side  views  of  an  object.    Fig.  199. 
Required:     To  draw  the  top  and  front  half  section  views  of 
the  object  shown  in  Fig.  199.    Scale,  half  size. 


CHAPTER  V 
ADVANCED  DRAWING 

PROSPECTUS 

The  first  year's  work  outlined  in  Chapters  I,  II,  III,  and  IV 
are  intended  to  give  opportunity  for  a  thorough  grounding  in 
the  fundamentals  of  the  theory  and  practice  of  drawing.  The 
second  year's  work  outlined  in  this  and  the  succeeding  chapter 
assumes  a  knowledge  of,  and  skill  in,  the  work  of  the  preceding 
year.  With  this  knowledge  and  skill  as  a  foundation  the  aim  of 
this  chapter  is  to  furnish  applications  of  principles  in  a  broader 
and  more  general  way  and  to  introduce  various  details  such  as 
conventional  sections,  screw  threads,  etc. 


SHEET  METAL  PATTERNS 
PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  24 

Development  of  a  Surface.  The  student  is  familiar  with 
many  articles  made  of  sheet  metal — tin,  zinc,  galvanized  iron, 
etc.  An  examination  of  these  objects,  such  as  pails,  cups,  pans, 
etc.,  will  make  it  clear  that  some  of  them  were  made  from  metal 
cut  from  flat  sheets  and  rolled  or  bent  into  particular  forms. 
The  student  will  recognize  the  geometrical  solids — prism,  cyl- 
inder, cone,  etc.,  as  the  bases  for  many  of  these  forms.  For 
example,  an  ordinary  tomato  can  is  in  the  form  of  a  cylinder. 
Before  an  object  of  this  kind  can  be  cut  from  a  sheet  of  metal 
a  pattern  must  be  made  which,  when  rolled  up,  will  give  the 
correct  form. 

189 


190 


MECHANICAL  DRAWING 


To  construct  this  pattern  the  object  is  imagined  rolled  on  a 
flat  surface,  such  as  that  of  the  drawing  board,  until  the  entire 
surface  of  the  solid  has  come  in  contact  with  the  plane  surface. 
Example :  In  Fig.  200  the  prism  was  rolled  until  each  of  its  faces 


FIG.  200.  EOLLING  A  PRISM  TO 
OBTAIN  THE  DEVELOPMENT  OF  ITS 
LATERAL  SURFACE 


FIG.  201.  ORTHOGRAPHIC  VIEWS 
AND  DEVELOPMENT  OF  THE  LATERAL 
SURFACE  OF  A  PRISM 


came  into  contact  with  the  board.  The  prints  of  these  faces  are 
shown.  If  the  whole  figure  a,b,  c,  d  were  cut  out  of  the  paper 
and  folded  up  on  the  lines  representing  the  edges  of  the  prism 
the  result  would  be  a  prism  like  the  original. 

Fig.  201  shows  two  views  of  a  square  prism  with  the  develop- 
ment of  the  lateral  surface.  It  is  evident  from  the  orthographic 
views  that  the  edges  of  the  bases  are  at  right  angles  to  the  lateral 
edges.  When  this  is  the  case  each  face  is  a  rectangle  which  is 
represented  in  the  development  by  a  rectangle  equal  to  that  of 
one  side  of  the  prism.  When  these  rectangles  are  joined  to- 
gether as  they  are  when  the  surface  is  imagined  unrolled,  the 
edges  of  the  bases  will  form  straight  lines.  Example :  Line  a  a. 
Fig.  201. 

The  steps  in  the  construction  of  the  pattern  are  as  follows : 

1.  Draw  two  parallel  lines  at  a  distance  apart  equal  to  the 
length  of  the  prism.    It  is  preferable  to  project  these  lines  from 
the  orthographic  view  as  in  Fig.  201. 

2.  Lay  off  with  the  dividers  on  one  of  these  lines  distances 
equal  to  the  widths  of  the  sides  of  the  prism,  taken  in  consecutive 


ADVANCED  DRAWING 


191 


order,  as  ab,  b  c,  c  d,  d  a.  Fig.  201.  For  the  square  prism  these 
distances  are  all  equal.  For  a  rectangular  prism  these  distances 
would  not  be  equal;  hence  care  must  be  taken  to  lay  off  the  dis- 
tances in  consecutive  order 


*  * 

> 


FIG.  202.    FURNACE  HEAT  PIPE 


DATA  FOR  DRAWING  PLATE  24 

Given:  Two  orthographic  views  of  a  rectangular  furnace 
heat  pipe.  Fig.  202. 

Required:  To  draw  a  pattern,  quarter  size,  from  which 
this  pipe  could  be  made,  or  any  similar  object  assigned  by  the 
instructor. 


Instructions : 

1.  Draw  the  two  given  orthographic  views. 

2.  Make  a  construction  similar  to  that  shown  in  Fig.  201.    In 
this  case  the  widths  of  adjacent  faces  are  not  equal.    The  width 
of  each  face  should  be  transferred  to  the  pattern  with  the  dividers 
from  the  top  view  starting  at  one  corner  and  continuing  around 
the  top  view  until  the  same  corner  is  reached. 

Beginning  at  this  point  in  the  course  the  lettering  plates  are 
made  up  of  lower  case  letters  and  numerals. 


192 


MECHANICAL  DRAWING 


SLOPE 


STROKES 


I  UNIT 


I 


STROKES 


/III! 


Illll 


11 

Tft= 


-L..L 


I 


2. 


inn 


m. 


Illll 

1L 


'111 


a 

Illll 


i 


i 


7~/r- 


Illll 


7SY 


///- 


/7"" 


///// 


lull 


illll 


HUH 


FIG.  203.    INCLINED  CAPITAL  LETTERS 


ADVANCED  DRAWING 


193 


-LJ 


STROKES 


Ill 


L 


//// 


"rr 


IIJIJI 


1111 


'Iflfl 


T///7 


mL 

TmWi 


//If/' 


Fiu.  204.    INCLINED  CAPITAL  LETTERS 


194  MECHANICAL  DRAWING 

PBEPABATOEY  INSTEUCTIONS  FOE  LETTEBOTG  PLATE  24 

The  Slope  of  the  inclined  letters  is  equal  to  that  of  the 
hypotenuse  of  a  right  triangle,  the  vectical  leg  of  which  is  two 
and  one-half  units  long  and  the  horizontal  leg  one  unit  long. 
Fig.  203. 


1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1  = 
444444  I4U  4114  441  141  = 

777777  174  147  4711  4177  = 
222222  1247  1724  22274  = 
555555  1572  5522  14725  = 


FIG.  205.    LETTERING  PLATE 

Lettering  in  Ink.  The  following  list  of  plates  will  be  made 
in  ink  directly  on  tracing  cloth.  A  list  of  materials  needed  and 
directions  for  lettering  in  ink  are  given  for  Plate  11  of  the 
vertical  Gothic  letters. 

DATA  FOR  LETTERING  PLATE  24= 

Given:    Plate  24  to  reduced  size.    Fig.  205. 
Required:    To  make  the  plate  to  an  enlarged  scale. 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  25 

A  somewhat  more  difficult  pattern  to  lay  out  than  the  one  just 
drawn  is  illustrated  by  a  square  pipe  cut  away  at  an  angle  to  meet 
another  pipe  to  form  an  elbow.  Fig.  206.  The  edges  of  the  lower 
base  are  at  right  angles  to  the  vertical  edges  and  will  therefore 


ADVANCED  DRAWING 


195 


unfold  into  a  straight  line.  The  lengths  of  these  lines  may  be 
taken  from  the  end  view  of  the  pipe  and  laid  off  on  the  pattern. 
It  is  evident  in  this  case  that  not  all  of  the  vertical  edges  are  of 


FIG.  206.   TYPE  PROBLEM.   DEVELOPMENT  OF  SQUARE  PIPE  CUT  AT  AN  ANGLE 

the  same  length.  Their  true  lengths  are  shown  in  the  front  view 
and  may  be  transferred  to  the  pattern  by  drawing  horizontal 
lines  from  it  to  the  pattern  as  shown  in  Fig.  206.  The  ortho- 
graphic views,  also,  show  that  two  of  the  edges  of  the  slanting 
base  are  horizontal  and  the  other  two  inclined.  The  lines  a  b,  b  e, 
c  d,  and  d  a  are  drawn,  connecting  points  a,  b,  c,  d,  which  should 
be  located  in  consecutive  order. 


r-* 


J 


FIG.  207.    EECTANGULAR  PIPE 


DATA  FOR  DRAWING  PLATE  25 

Given:  Two  orthographic  views  of  an  elbow  for  a  rec- 
tangular pipe.  Fig.  207. 

Required:  To  draw  a  pattern,  quarter  size,  from  which 
the  pipe  could  be  made,  or  any  similar  object  assigned  by  the 
instructor. 


196  MECHANICAL  DRAWING 

1.  Draw  two  given  orthographic  views  and  make  a  construc- 
tion similar  to  that  shown  in  Fig.  206. 


PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  25 

Curved  Strokes.  The  6  and  9  have  the  same  cval  outline 
as  the  0.  This  form  should  be  kept  in  mind  w'.lle  drawing  the 
6  and  9. 

Given:     Plate  25  to  reduced  size.    Fig.  208. 

Required:     To  make  the  plate  to  an  enlarged  scale. 


-000000  1470  7104  20504  = 
=  666666  1626  6064  65276  = 
=  999999  1929  4956  91979  = 

-L5[9I5J_17_5J_     _7     _&      J_- 
-16    64    64    2    4    16    64   4     16     16      2  - 

:  1116  4701  2196    1245  790= 


FIG.  208.    LETTERING  PLATE 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  26 

The  cylinder  is  a  very  common  form  in  sheet  metal  work. 
Many  cans,  pails,  pipes,  etc.,  are  cylindrical  in  form.  When  the 
base  of  a  cylinder  is  at  right  angles  to  its  axis,  the  base  will  unroll 
into  a  straight  line.  Fig.  209.  The  length  of  this  line  must  be 
found  by  dividing  the  circle  representing  the  end  view  of  the 
cylinder  into  a  number  of  small  parts  and  stepping  off  these 
lengths  with  the  dividers  on  a  straight  line.  Each  distance 
transferred  is  the  chord  of  the  arc  between  two  points.  These 
divisions  must,  therefore,  be  small  enough  so  that  the  straight 


ADVANCED  DRAWING 


197 


line  distance  between  consecutive  points  is  not  greatly  different 
from  the  distance  measured  between  these  points  on  the  circle, 
or  the  arc  distance.  These  divisions  are  usually  made  equal  so 
that  one  setting  of  the  dividers  is  sufficient  for  stepping  off  all 
the  lengths. 


Z    3    4    S    6     7    8    9    t0    //    1 


FIG.    209.    TYPE   PROBLEM.    DEVELOPMENT   OF   CYLINDRICAL   SURFACE 

Eight  points  equally  spaced  on  the  circumference  are  very 
easily  obtained  with  the  45°  triangle,  or  twelve  points  may  be 
obtained  with  the  30°-60°  triangle  as  shown  in  Fig.  210. 

Sixteen  points  equally  spaced  may  be  obtained  by  subdividing 
each  of  the  eight  divisions  with  the  dividers. 


FIG.  210.    DIVIDING  A  CIRCLE  INTO  8  OR  12  PARTS  WITH  TRIANGLES 


DATA  FOB  PLATE  26 

Given:  Two  orthographic  views  of  a  bench  oil-waste  cup. 
Fig.  211. 

Required:  To  draw  a  pattern  from  which  the  cup  can  be 
made,  or  any  similar  object  assigned  by  the  instructor. 

Instructions:  Draw  the  two  orthographic  views  and  make  a 
construction  similar  to  that  shown  in  Fig.  209. 


198 


MECHANICAL  DRAWING 


PREPARATORY    INSTRUCTIONS    AND    DATA    FOR    LETTERING 

PLATE  26 

The  two  ovals  of  the  8  have  their  major  axes  at  45°.     The 
same  combination  of  ovals  is  the  basic  form  for  the  3. 


FIG.  211.    OIL  WASTE  CUP 


=  33333333  323  435 3  36 3 
=  88888888  1834  687  585 
~ssssssssss/473  386  83 

7359      3      11 
.SS55SS      Q     4     Q     ,6     64     4     I6 

=  1830    1492  123456789 


FIG.  212.    LETTERING  PLATE  26 


Given:      Plate  26  to  reduced  size.    Fig.  212. 
Required:     To  make  the  plate  to  an  enlarged  scale. 
The  strokes  for  the  S  are  given  in  Fig.  238. 


ADVANCED  DRAWING 


199 


PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  27 

If  a  cylindrical  object  is  cut  away  at  an  angle,  as  in  the  case 
of  the  elbow  in  Fig.  213,  the  end  which  is  cut  will  not  roll  out 
into  a  straight  line.  The  curved  line  into  which  it  will  unroll 
must  be  determined  by  locating  a  number  of  points  through 
which  it  passes.  This  may  be  done  by  drawing  lines  in  the 
orthographic  view  which  represent  elements  or  lines  in  the  cyl- 
indrical surface  parallel  to  the  axis  of  the  cylinder.  For  con- 
venience these  lines  should  be  drawn  perpendicularly  up  from 
the  points  located  in  the  base  circle.  The  length  of  each  of  these 


FIG.  213.    DEVELOPMENT  OP  CYLINDRICAL  SURFACE  CUT  AT  AN  ANGLE 


lines  from  the  base  up  to  the  inclined  line  is  the  length  of  a  cor- 
responding line  to  be  located  in  the  pattern,  because  it  is  shown 
in  its  true  length. 

Vertical  lines  are  drawn  in  the  pattern  from  the  points 
stepped  off  in  the  base.  These  lines  represent  the  ones  drawn 
in  the  surface  of  the  cylinder.  The  length  of  these  lines  may 
be  transferred  from  the  orthographic  view  to  the  pattern  with 
the  dividers  or  by  drawing  horizontal  lines  across  from  the 
orthographic  view  as  in  Fig.  213.  Example:  Line  a  7  in  the 
orthographic  view  is  equal  to  a  7  in  the  pattern.  Here  again  it 
is  necessary  that  these  lengths  be  transferred  in  consecutive 
order. 


200 


MECHANICAL  DRAWING 


When  both  ends  of  the  cylinder  are  cut  at  an  angle  as  in 
Fig.  214,  neither  end  will  develop  into  a  straight  line.  For  the 
purpose  of  determining  the  length  of  the  pattern  a  line  such  as 
a  b  must  be  drawn  in  to  represent  an  imaginary  base  which  is  at 
right  angles  to  the  axis  of  the  cylinder.  The  lengths  of  the 
division  from  the  circular  view,  A,  are  then  stepped  off  on  a 


FIG.  214.     TYPE  PROBLEM.     DEVELOPMENT  OF  CYLINDRICAL  SURFACE  CUT  AT 

BOTH  ENDS 

line  representing  this  imaginary  base,  c  d,  Fig.  214.  The  points 
on  the  curved  lines  in  the  development  are  located  by  using  this 
imaginary  base  to  measure  from.  If  the  base  is  centrally  located 
between  the  two  cut  ends,  points  on  both  curves,  on  any  one  ele- 
ment, may  be  located  with  one  measurement,  as  in  the  case  shown 
in  Fig.  214. 

DATA  FOR  DRAWING  PLATE  27 

Given:     Two  orthographic  views  of  the  objects  shown  in 
Figs.  215,  216,  and  217. 


ADVANCED  DRAWING 


.   201 


Required :  To  draw  a  pattern  for  one  of  the  objects  shown 
in  Fig.  215,  216,  or  217,  or  any  similar  object  as  assigned  by  the 
instructor. 


FIG.  215.    FLOUR  SIFTER 


FIG.  216.     SCOOP 


Instructions:     D*aw  the  orthographic  views  and  make  a  con- 
struction similar  to  that  shown  in  Fig.  215,  216,  or  217. 


202 


MECHANICAL  DRAWING 


PREPARATORY  INSTRUCTIONS  AND  DATA  FOR  LETTERING 

PLATE  27 

Spacing  of  Letters.    Observe  carefully  the  spacing  of  the 


FIG.  217.    FIVE  PIECE  ELBOW 


STRC 

)KES 

1 

2 

/ 

~j 

IT 

^ 
^ 

—  // 

^ 

-/ 

n 

7 

STRC 

)KES 

1 

2 

3E 

fi~ 

/ 

,£> 

f 

3  

"=[&"" 

/ 

n 

FIG.  218.    LETTERING  PLATE.    1,  i,  t,  v,  y 

letters  in  the  words.    Correct  spacing  is  as  essential  as  correct 
forms. 


ADVANCED  DRAWING  203 

Given:     Plate  27  to  reduced  size.    Fig.  219. 
Required:     To  make  the  plate  to  an  enlarged  scale. 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  28 

Another  geometrical  form  commonly  found  in  sheet  metal 
work  is  the  cone.  If  the  cone  were  rolled  on  a  flat  surface  its 
surface  would  come  in  contact  with  an  area  as  shown  in  Fig.  220. 


I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  J    = 

/  /  /  /  /  /  /  /  /  /  ///  ill  ill  ill  ill  ill  = 
//////////  ////  ////  ////  //  ////  //z 
vvvvvvvv  liv  vilt  liv  vilt  till  ~_ 

y  y  y  y  y  y  y  y  ////  ivy 


FIG.  219.    LETTERING  PLATE  27.    1,  i,  t,  v,  y 

The  vertex  would  remain  at  a  fixed  point.  Since  all  straight 
lines  drawn  in  the  surface  of  the  cone  from  the  vertex  to  the  base 
circle  are  equal  in  length,  the  base  circle  will  unroll  into  an  arc 
with  a  radius  equal  to  the  true  distance  from  the  vertex  to  a 
point  in  the  base  circle.  Fig.  220.  The  length  of  this  arc  is 
equal  to  the  circumference  of  the  base  circle  of  the  cone  and  may 
be  laid  off  by  dividing  the  orthographic  view  of  the  base  circle 
into  a  number  of  small  divisions  as  described  for  the  cylinder, 
page  197.  These  lengths  are  then  transferred  to  the  arc  with 
the  dividers. 

The  pail  shown  in  Fig.  221  is  not  a  complete  cone.  It  is 
therefore  necessary  to  draw  a  second  arc  to  represent  the  circular 
bottom  of  the  pail. 


204 


MECHANICAL  DRAWING 


DATA  FOR  DRAWING  PLATE  28 

Given:     Two  orthographic  views  of  the  objects  shown  in 
Figs.  222  and  223. 


FIG.  220.     ROLLING  A  COXE  TO  OBTAIN  THE  DEVELOPMENT  OF  ITS  SURFACE 


Required:  To  draw  a  pattern  for  one  of  the  objects  shown 
in  Fig.  222  or  223,  or  any  similar  object  as  assigned  by  the 
instructor. 

Instructions:  Draw  the  orthographic  views  and  make  a  con- 
struction for  the  pattern  similar  to  that  shown  in  Fig.  221. 


ADVANCED  DRAWING 


FIG.  221.    TYPE  PROBLEM.    PAIL 


FIG.  222.     CREAM  DIPPER 


206 


MECHANICAL  DRAWING 


DATA  FOR  LETTERING  PLATE  28 

Given:    Plate  28  to  reduced  size.    Fig.  225. 
Bequired:    To  make  the  plate  to  an  enlarged  scale. 


"    FIG.  223.    FUNNEL 


± 


STROKES 


STRC 

)KES 

1 

2 

..  ./.... 

l.Tj.... 

$ 

=  wy 

—  KM.... 

Jh 

£» 

t 

/v—  ' 

Ji 

j  

iiir/xiv." 

:".^f"". 

:'/ 

i 

FIG.  224.    LETTERING  PLATE,    w,  k,  z,  x,  j,  f 


ADVANCED  DRAWING  207 

PREPAEATOEY  INSTRUCTIONS  FOR  DRAWING  PLATE  29 

The  section  of  a  right  conical  surface  cut  at  right  angles  to 
the  axis  of  the  cone  will  develop  into  the  arc  of  a  circle  as  shown 


I  w  w  w  w  w  will  wily  wilt  twit  it  ~ 
z  k  k  k  k  k  k  kilt  kitty  z  z  z  z  z  t/zl 
I.X  x  x  x  x  x  vix  xylyl  viz  xylyl  ill f 
-////' /'/'  jilt  Jill  Jill  jilt  JHI  jilt  //  = 
^ffffff  fizz  jiffy  flit  fizz  fifty  = 


FIG.  225.    LETTERING  PLATE,    w,  k,  x,  j,  f 

in  the  case  of  the  bottom  of  the  pail,  Fig.  221.  When  the  conical 
surface  is  cut  on  a  slant  as  shown  in  Fig,  226,  the  distances  from 
the  vertex  to  points  on  the  cut  are  not  equal  and  therefore  the  cut 
edge  will  not  roll  out  into  an  arc  of  a  circle.  Points  on  the 
curved  line  into  which  this  cut  edge  will  develop  may  be  located 
by  drawing  in  the  elements  or  lines  in  the  conical  surface  from 
the  vertex  to  points  in  the  base  circle.  These  elements  may  be 
located  in  the  pattern  by  joining  the  vertex  with  points  on  the 
arc  of  the  base  corresponding  to  the  points  in  which  these  lines 
meet  the  base  circle  of  the  cone. 

This  construction  is  illustrated  in  Fig.  227,  where  the  points 
in  which  the  elements  pass  through  the  cut  edge  of  the  cone  are 
located  in  the  development  by  finding  their  true  distances  on  the 
elements  from  the  vertex  (see  horizontal  lines  in  front  view)  and 
transferring  these  lengths  to  the  corresponding  lines  in  the  devel- 
opment. This  may  be  done  with  the  dividers  or  by  swinging 
arcs  with  the  compass  as  shown  in  the  figure. 


208 


MECHANICAL  DRAWING 


The  true  lengths  of  the  contour  elements  of  the  cone  are 
shown  in  the  front  view,  Fig.  227,  in  oe  and  od.    None  of  the 


QKtt  10    9      6      7      ff     S    4 

FIG.  226     DEVELOPMENT  OF  A  CONE  CUT  AT  AN  ANGLE  TO  ITS  Axis 

other  elements  show  in  their  true  length,  although  they  are  known 
to  be  equal  in  length  to  o  e  and  o  d. 


ADVANCED  DRAWING 


209 


In  order  to  find  the  distance  from,  the  vertex  to  a  point  such 
as  a  on  an  element  a  construction  is  necessary.  The  student 
should  try  to  fix  in  mind  the  principle  on  which  this  construction 
is  made,  which  is  as  follows.  Since  any  element  o  c  is  equal  in 
length  to  o  d  it  may  be  imagined  turned  around  into  coincidence 
with  o  d  by  keeping  the  end  c  always  in  the  base  circle.  Thus  the 


c    at 


FIG.  227.    ILLUSTRATING  METHOD  OF  OBTAINING  TRUE  LENGTHS  OF  ELEMENTS 

point  c  moves  through  an  arc  e  d.  The  point  at  the  other  end  of 
the  line  o  c  remains  fixed,  but  any  point,  such  as  a  between  o 
and  c  will  move  on  an  arc  a  b.  Thus  when  o  c  is  brought  into 
coincidence  with  o  d  the  true  length  of  o  c  is  shown  in  o  d  and  the 
true  length  of  any  part  of  it,  such  as  o  a,  is  shown  in  o  b.  Notice 
that  the  base  circle  of  the  cone  appears  as  a  straight  horizontal 
line  e  d,  Fig.  227,  and  also  that  the  arc  a  b  appears  as  a  straight 
horizontal  line  in  the  front  view  of  the  cone.  With  this  point 
clearly  in  mind  it  will  be  evident  that  to  find  the  length  of  o  a  it 
is  only  necessary  to  draw  the  horizontal  line  ab  as  construction. 

DATA  FOB  DRAWING  PLATE  29 


Given:    The  orthographic  views  of  the  objects  shown  in 
Figs.  228  and  229. 


210 


MECHANICAL  DRAWING 


Required :  To  draw  a  pattern  for  one  of  the  objects  shown 
in  Fig.  228  or  229,  or  any  similar  object  assigned  by  the 
instructor. 

Instructions:  Draw  the  orthographic  views  and  make  a  con- 
struction for  the  pattern  similar  to  that  shown  in  Fig.  226. 


FIG.  228.    VENTILATOR  PIPE 


FIG.  229.    SCALE  SCOOP 

DATA  FOR  LETTERING  PLATE  29 

Given:     Plate  29  to  reduced  size.    Fig.  231. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


ADVANCED  DEAWING 


STROKES 


l£ 


FIG.  230.    LETTERING  PLATE,    r,  h,  n,  m 


211 


r  r  r  r  r  r  r  kirk  vitrify  kirts  six 
h  h  h  h  h  h    hilt  whirl  whist  his 
n  n  n  n  n  n   hint  lynx  hint  lynx 
m  m  m  m   mink  hymn  milk  hint 


65'- 4 


FIG.  231.    LETTERING  PLATE  29.    r,  h,  n,  m 


212 


MECHANICAL  DRAWING 


PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  30 

If  a  pyramid  were  rolled  on  a  flat  surface  its  faces  would 
come  in  contact  with  triangular  areas  such  as  shown  for  the 
square  pyramid  in  Fig.  232.  In  this  case  there  are  four  triangles. 
For  a  hexagonal  pyramid  there  would  be  six  triangles,  etc.  The 
length  of  the  edges  of  the  pyramid  from  the  vertex  to  the  corner 
of  the  base  are  all  equal.  Therefore  if  an  arc  of  radius  equal  to 
their  length  were  drawn  these  lines  would  all  end  in  the  arc.  The 
sides  of  the  base  of  the  pyramid  will  appear  in  the  pattern  as 


FIG.  232.  ROLLING  A  PYRAMID  TO 
OBTAIN  THE  DEVELOPMENT  OF  ITS 
LATERAL  SURFACE 


I       c 

FIG.  233.     TYPE  PROBLEM.     DEVEL- 
OPMENT OF  A  SQUARE  PYRAMID 


chords  of  this  arc.  In  the  case  of  the  square  pyramid  as  shown 
in  Fig.  233,  none  of  the  edges  from  the  vertex  to  the  base  are 
shown  in  their  true  length.  A  construction  such  as  that  described 
for  finding  the  lengths  of  the  elements  of  the  cone  must  be  made 
for  finding  the  lengths  of  these  edges.  Referring  to  Fig.  233r 
the  base  of  the  pyramid  is  inscribed  in  a  circle  which  corresponds 
to  the  base  circle  of  the  cone.  If  the  edge  oc,  for  example,  is 
imagined  turned  as  was  the  element  of  the  cone,  into  a  position 
corresponding  to  the  contour  element  of  the  cone,  it  will  show 
in  its  true  length  in  the  front  view,  o  d,  Fig.  233,  therefore 
represents  the  true  length  of  the  edge  o  c.  With  this  length  as  a 
radius,  an  arc  may  be  drawn  and  the  points  representing  the 
lower  corners  of  the  pyramid  may  be  located  on  it  by  stepping 
off  lengths  equal  to  the  side  of  the  base,  such  as  ec. 


ADVANCED  DRAWING 


213 


DATA  FOB  DRAWING  PLATE  30 

Given:     The  orthographic  views  of  the  object  shown  in 
Fig.  234. 


FIG.  234.    END  FOE  GRAIN  CONVEYOR 


STROKES 


=/ 


FIG.  235.    LETTERING  PLATE,    n,  o,  c,  e 


214  MECHANICAL  DRAWING 

Required:  To  draw  a  pattern  for  the  object  shown  in  Fig. 
234  or  any  similar  object  as  assigned  by  the  instructor. 

Instructions :  Draw  the  orthographic  views  and  make  a  con- 
struction for  the  pattern  similar  to  that  shown  in  Fig.  233. 


u  u  u  u  u  u  u    hum  tumult  funny 
ooooooo  moon  form  fourth 
c  c  c  c  c  c  c   lock  column  corks 
e  e  e  e  e  e  e   clever  come  fewer 
68 j'  29'-Ol"  /3/j"      997' -8 


FIG.  236.    LETTERING  .  PLATE  30.    u,  o,  e,  e 

PEEPAEATOEY  INSTETTCTIONS  AND  DATA  FOE  LETTEEINO 

PLATE  30 

Curved  Strokes.  The  major  axes  of  the  oval  letters  of  this 
plate  are  in  the  direction  of  the  slope. 

Given:    Plate  30  to  reduced  size.    Fig.  236. 
Required:    To  make  the  plate  to  an  enlarged  scale. 

PEEPAEATOEY  INSTEUCTIONS  FOE  DEAWING  PLATE  31 

The  true  length  of  the  edge  of  a  pyramid  cut  at  a  slant  is 
found  as  previously  described.  Finding  the  true  length  of  the 
edges  from  the  vertex  to  the  point  where  the  edge  strikes  the  cut 
involves  the  same  theory  discussed  in  connection  with  the  pattern 
for  the  cone,  page  209,  Fig.  227  The  construction  is  also  the 
same. 


ADVANCED  DRAWING 


215 


DATA  FOR  DRAWING  PLATE  31 

A  problem  for  this  plate  may  be  supplied  by  the  instructor 
if  desired. 


FIG.  237.     DEVELOPMENT  OF  PYRAMID  CUT  AT  AN  ANGLE  TO  ITS  Axis 


PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  31 

Curved  Strokes.     The  major  axes  of  the  ovals  of  this  plate 
make  45°  with  the  horizontal. 


DATA  FOR  LETTERING  PLATE  31 

Given:     Plate  31  to  reduced  size.    Fig.  239. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  32 

Intersection  of  Surfaces.  The  objects  thus  far  considered 
have  been  of  the  form  of  geometrical  solids.  There  is  another 
class  of  patterns  which  involves  the  laying  out  of  the  line  where 


216 


MECHANICAL  DRAWING 


STROKES 


7/7= 


T/7- 


STROKES 


— /- 


FIG.  238.    LETTERING  PLATE,    a,  d,  q,  g,  b,  p,  s 


z  a  a  a  a  a  a  crank  moke  chairs  ~ 
z  d  d  d  d  d  d  round  drain  rods  at^_ 
~  q  q  q  q  q  quail  g  g  g  g  ground  ~ 
z  b  b  b  b  b  b  bearing  block  blade  ~ 
~  p  p  p  p  p  p  pipe  faceplate  shapes 


FIG.  239.    LETTERING  PLATE  31.    a,  d,  q,  g,  b,  p,  s 

the  surfaces  of  two  solids  meet  or  intersect.    An  example  of  the 
intersection  of  two  prisms  is  afforded  in  the  case  of  the  roof  of 


ADVANCED  DRAWING 


217 


a  house,  as  shown  in  Fig.  240.  The  line  of  intersection  is  the  line 
abc  where  the  roofs  meet.  It  is  quite  evident  that  this  broken 
line  abc  lies  in  the  surface  of  the  main  roof  and  also  in  the  sur- 
face of  the  dormer  roof,  or,  in  other  words,  it  is  a  broken  line 
which  is  common  to  both  roofs.  This  illustrates  the  general  defi- 
nition of  a  line  of  intersection,  which  is  as  follows :  The  line  of 


FIG.  240.    ILLUSTRATION  OF  AN  INTERSECTION 

intersection  behveen  two  surfaces  is  the  line  which  lies  in  both 
surfaces.  In  the  following"  discussion  of  the  laying  but  of  pat- 
terns of  objects  containing  intersecting  surfaces,  this  definition, 
if  kept  clearly  in  mind,  will  help  in  grasping  the  principles  on 
which  the  methods  are  based. 

In  Fig.  241  is  shown  the  orthographic  view  of  a  cylinder  inter- 
secting a  square  prism.  In  this  case  the  right  side  view  is  unnec- 
essary for  the  purpose  of  laying  out  a  pattern.  It  is  drawn  to 
show  the  method  of  constructing  the  line  of  intersection  in  this 
view,. as  in  some  cases  it  will  be  necessary  to  draw  a  view  corre- 
sponding to  this  one.  It  also  gives  a  better  idea  of  the  method 
by  which  the  points  on  the  line  of  intersection  are  located  for 
transferring  to  the  pattern. 

Development  of  the  Cylindrical  Surface.  As  in  Plate  26,  the 
edge  of  the  upper  base  of  the  cylinder  which  is  at  right  angles 
to  the  axis  of  the  cylinder  will  develop  into  a  straight  line.  The 
length  of  this  line  may  be  determined,  as  before,  by  dividing  the 


218 


MECHANICAL  DRAWING 


base  circle  into  a  number  of  equal  small  divisions  and  stepping 
them  off  with  the  dividers.  To  obtain  the  development  of  the  line 
of  intersection,  elements  are  drawn  in  the  surface  of  the  cylinder, 
preferably  from  the  points  already  located  in  the  base  circle. 
Lines  are  then  drawn  in  the  patterns  to  represent  them.  Their 
lengths  may  be  transferred  from  the  orthographic  views  by  means 


Pattern  for  one-ha/f  of  cylinder)  / 


FIG.  241.    TYPE  PROBLEM.    INTERSECTION  OF  A  SQUARE  PRISM  AND  A 

CYLINDER 


of  the  dividers  or  projected  by  horizontal  lines  as  shown  in 
Fig.  241.' 

The  pattern  for  the  entire  surface  of  the  prism  is  laid  out  as 
in  Plate  24.  The  hole  opening  into  the  cylinder  or  the  line  of 
intersection  is  determined  in  the  pattern  as  follows :  In  the  front 
view  the  lateral  surfaces  of  the  prism  are  s"een  edgewise,  and  con- 
sequently the  points  in  which  the  cylinder  strikes  the  surfaces 
of  the  prism  are  seen  in  the  points  where  the  lines  representing 
these  elements  cross  the  lines  representing  the  surfaces  of  the 
prism.  Example :  b  is  the  point  in  which  the  element  a  b  of  the 


ADVANCED  DRAWING 


219 


cylinder  strikes  the  surface  of  the  prism.  If  a  line  is  drawn  in 
the  surface  of  the  prism,  through  point  b  and  parallel  to  the 
lateral  edges  of  the  prism,  the  distance  of  this  line  from  the  edge 
of  the  prism  may  be  located  on  the  pattern.  The  true 


FIG.  242.    EOOF  CAP  AND  VENTILATOR 


•10  D- 


FIG.  243.    SOLDERING  STOVE 

length  of  this  line,  which  is  shown  in  the  top  view,  may 
be  transferred  to  the  pattern  with  the  dividers  or  projected  from 
the  orthographic  view  as  indicated  in  the  drawing.  A  similar 
construction  should  be  made  for  the  other  points  on  the  line  of 
intersection. 


DATA  FOB  DRAWING  PLATE  32 

Given:     The  orthographic  views  of  the  objects  shown  in 
Figs.  242  and  243. 


220  MECHANICAL  DRAWING 

Required:  To  draw  the  orthographic  views  and  construct 
patterns  for  the  object  shown  in  Fig.  242  or  243,  or  any  similar 
object  as  assigned  by  the  instructor. 


PREPARATORY  INSTRUCTIONS  FOR  LETTERING  PLATE  32 

Composition.  In  the  following  composition  plates  the  spacing 
of  letters  and  words  should  be  given  as  much  consideration  as  the 
forms  of  the  letters.  The  student  should  strive  to  produce  a  good 
general  effect  in  the  plate, 


Drill  ^  Ream  I"  Bore  2"  Holes 
/0  Suit  Motor  Used  End  of  stud 
/0  be  flattened  and  cast  in  part 
/   Use  Fillers  513  to  Allow  A// 
Gears  to  Mesh  Properly    Head 


FIG.  244.    LETTERING  PLATE  32 


DATA  FOR  LETTERING  PLATE  32 

Given:     Plate  32  to  reduced  size.    Fig.  244. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  33 

The  laying  out  of  patterns  for  the  surfaces  of  two  intersecting 
cylinders  involves  the  same  general  principles  as  described  for 


ADVANCED  DRAWING 


221 


the  intersection  of  the  prism  and  cylinder  in  Plate  32.  The  base 
of  the  smaller  of  the  two  cylinders  should  be  divided  into  a  num- 
ber of  equal  parts  and  its  surface  developed  as  before. 

The  entire  surface  of  the  larger  cylinder  is  laid  out  and  the 
points  in  which  the  elements  of  the  smaller  cylinder  strike  the 


FIG.  245.    TYPE  PROBLEM:.     INTERSECTION  OF  Two  CYLINDERS 

surface  are  located  by  drawing  elements  of  the  larger  cylinder 
through  these  points.  The  spacing  of  these  elements  is  obtained 
by  stepping  off  the  arcs  a  b,  b  c,  etc.,  Fig.  245,  between  the  points 
representing  these  elements  in  the  end  view  (top  view  in  this 
case)  of  the  cylinder. 


DATA  FOR  DRAWING  PLATE  33 

Given:  The  orthographic  views  of  the  objects  shown  in 
Figs.  246  and  247. 

Required:  To  draw  the  orthographic  views  and  construct 
patterns  for  the  objects  shown  in  Fig.  246  or  247,  or  any  similar 
object  assigned  by  the  instructor 


222 


MECHANICAL  DRAWING 


50- 

Ficf.  246.    EAVE  TROUGH  AND  DOWN  SPOUT 


FIG.  247.    FURNACE  SMOKE  PIPE 

DATA  FOR  LETTERING  PLATE  33 

Given:     Plate  33  to  reduced  size.    Fig.  248. 
Eequired:     To  make  the  plate  to  an  enlarged  scale. 


ADVANCED  DRAWING  223 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  34 

In  the  preceding  plates,  elements  were  first  drawn  in  the  cylin- 
der to  strike  the  surface  of  the  other  solid.  In  the  construction 
of  the  intersection  line  between  a  cylinder  and  cone,  example, 
Fig.  249,  elements  of  the  cone  are  first  drawn  striking  the  surface 
of  the  cylinder.  This  is  made  necessary  by  the  fact  that  the  cone 
has  a  slanting  surface  which  is  not  seen  edgewise  in  any  view, 
consequently  it  is  impossible  to  tell  where  elements  drawn  in  the 
surface  of  the  cylinder  strike  the  surface  of  the  cone. 


-2-IJX/9J  Rough  Round  Rods  z 
=  /-//  Bolts- 6^'  Long  Without  z 
zM//  &.  Check  Nut  Connecting  z 
z  Rod  Bearing  14  -  24  Flat  Head^ 
^Machine  Screw  Graphite  Paint~_ 


FIG.  248.     LETTERING  PLATE  33 

The  elements  of  the  cone  should  first  be  drawn  in  the  front 
view  and  in  such  a  manner  as  to  divide  the  circular  base  of  the 
cylinder  into  a  number  of  small  parts.  It  is  evident  that  these 
parts  cannot  all  be  equal  as  in  the  preceding  problems. 

Draw  the  top  views  of  these  same  elements  of  the  cone.  This 
is  done  for  element  ab  by  projecting  from  a  to  the  base  circle  of 
the  cone  in  the  top  view  to  determine  the  foot  of  the  element  ab 
in  the  top  view,  and  connecting  this  point  with  the  apex. 

Elements  should  now  be  drawn  in  the  surface  of  the  cylinder 
to  pass  through  the  points  in  which  the  elements  of  the  done  strike 
the  surface  of  the  cylinder.  Example :  c  in  the  top  view  is 
projected  from  the  point  c  in  the  front  view. 


224 


MECHANICAL  DRAWING 


The  other  points  on  the  intersection  are  located  in  the  top 
view  in  the  same  manner. 


The  surface  of  the  cylinder  may  now  be  developed  following 
the  usual  method.  Attention  is  again  called  to  the  fact  that  the 
elements  of  the  cylindrical  surface  are  not  equally  spaced.  It 


ADVANCED  DRAWING 


225 


will  therefore  be  necessary  to  step  off  each  division  separately, 
taking  care  to  place  them  in  consecutive  order  in  the  pattern. 
The  true  lengths  of  the  elements  from  the  base  to  the  line  of  inter- 
section are  shown  in  the  top  view  and  may  be  either  transferred 
to  the  pattern  with  the  dividers  or  projected  from  the  top  view 
as  shown  in  Fig.  249. 


I';G.  250.     OIL  RECEPTACLE 

The  entire  surface  of  the  arc  is  laid  out  in  the  pattern  by 
striking  an  arc  of  radius  equal  to  the  length  of  the  elements  of 
the  cone  and  stepping  off  on  this  arc  a  distance  equal  to  the  cir- 
cumference of  the  base  circle.  On  this  arc  are  located  the  feet 
of  the  elements  on  which  points  on  the  intersection  were  found, 
by  transferring  the  distances  between  the  feet  of  these  elements 
from  the  top  view  of  the  base  circle.  The  points  on  the  line  of 
intersection  are  located  on  these  elements  by  finding  the  true 
lengths  from  the  vertex  of  the  cone  to  the  line  of  intersection  for 
each  element.  The  construction  for  this  is  described  in  detail  on 
page  209. 

DATA  FOR  DRAWING  PLATE  34 

Given:  The  orthographic  views  of  the  objects  shown  in 
Figs.  250  and  251. 


226 


MECHANICAL  DRAWING 


Required:  To  draw  the  orthographic  views  and  make  a 
construction  for  the  pattern  of  the  objects  shown  in  Fig.  250, 
251,  or  any  similar  object  as  assigned  by  the  instructor. 

Instructions:  The  fact  that  the  cylinder  in  Fig.  250  is  larger 
in  proportion  to  the  cone  than  in  the  type  problem  makes  no  dif- 
ference in  the  principle  of  the  problem  or  the  method  used  in  its 
solution.  It  is  only  necessary  to  assume  a  base  for  the  cone  and  a 
vertex  as  indicated  by  the  dotted  lines. 


FIG.  251.    EXHAUST  HEAD 

In  the  object  shown  in  Fig.  251,  the  axis  of  the  cylinder  is 
parallel  to  the  axis  of  the  cone.  The  elements  of  the  cone  should 
always  be  drawn  first  in  the  view  in  which  the  cylindrical  surface 
shows  as  a  circle,  which  in  this  case  is  the  top  view. 


DATA  FOB  LETTERING  PLATE  34 

Given:     Plate  34  to  reduced  size.    Fig.  252. 
Required:    To  make  the  plate  to  an  enlarged  scale. 

A  Bill  of  Stock  is  a  tabulated  form,  such  as  the  bill  of  mate- 
rial, but  which  gives  the  rough  and  sometimes  the  finished  sizes 
for  each  different  piece  of  timber  and  the  number  of  each  size 
required,  together  with  a  list  of  all  other  materials  to  be  used  in 
the  project.  Such  a  tabulated  summary  makes  it  possible  to  cut 


ADVANCED  DRAWING  227 

all  stock  and  to  calculate  the  cost  of  all  materials  for  any  project 
in  wood.     Example :  Fig.  267  shows  a  bill  of  stock  for  a  table. 

Sectional  Views,  Very  often  a  drawing  is  not  clear  because 
the  interior  of  the  object  is  complex  or  because  a  part  of  it  is 
obscured  by  other  lines.  In  such  cases  the  object  may  be  repre- 


z  /' 'Drill  and  Ream  Holes  for  All  z 
^Pieces.  Spring  Must  Deflect  2"  z 
~  Factor  of  Safety  1, 5  Patterns  z 
z  I j  Core  for  Piece  No.  640139  = 
=  j'  Chain  (277  Links)  Material  z 


FIG.  252.    LETTERING  PLATE  34 

sented  more  clearly  if  a  portion  of  it  is  imagined  cut  away  to 
expose  the  hidden  part.  The  most  common  examples  of  this 
method  of  representation  are:  (1)  half -section  in  which  the 
object  is  cut  into  two  similar  parts  through  an  axis  of  symmetry, 
and  (2)  quarter-section  in  which  the  object  is  cut  in  to  the  center 
on  two  planes  at  right  angles.  These  sections  are  described  in 
detail  on  pages  98  and  99  and  illustrated  on  page  94. 

Other  methods  of  sectioning  may  be  used,  depending  upon  the 
form  of  the  object  or  part  which  it  is  desired  to  make  clear.  Fig. 
253  illustrates  a  case  where  the  section  is  taken  on  a  broken  line, 
A  0  B.  In  drawing  the  section  view,  the  cut  surface  0  A  is  con- 
sidered revolved  into  the  same  plane  with  O  B.  Fig.  254  illus- 
trates what  is  called  a  partial  section.  The  ragged  line  indicates 
that  a  part  of  the  shaft  has  been  broken  away. 

The  cross-section  of  an  object  is  often  given  by  showing  a 


228 


MECHANICAL  DRAWING 


revolved  section  in  one  of  the  views,  Fig.  255  or  265.  Where  the 
section  cannot  well  be  revolved  a  line  may  be  drawn  across  the 
view  of  the  part  at  the  place  where  the  section  is  taken  and  the 


Section  on  AOB 

FIG.  253.    BROKEN  LINE  SECTION 


TIG.  254.     PARTIAL  SECTION 

section  drawn  in  an  open  space  near  the  view.  Reference  should 
be  made  to  the  line  on  which  the  section  is  taken.  Fig.  256.  Such 
parts  as  spokes  or  arms  of  wheels,  solid  shafts  or  rods,  screws, 
bolts,  studs,  and  nuts  are  not  represented  as  cut  when  the  section 
plane  passes  through  their  axes.  Fig.  257.  Ribs  and  webs  are 


ADVANCED  DRAWING 


229 


not  sectioned  when  the  section  plane  is  parallel  to  their  lateral 
faces. 

When  a  section  is  taken  through  an  assembly,  adjacent  parts 
are  crosshatched  in  different  directions  to  aid  in  distinguishing 
one  from  another. 


FIG.  255.    REVOLVED  SECTION 

Various  combinations  of  lines  are  used  to  represent  sections  of 
different  materials.  No  standard  section  notation  has  ever  been 
universally  adopted.  It  is  customary  to  add  a  note  giving  the 


Section  A  A 


Sec f /on  63 


FIG.  256.    REMOVED  SECTIONS 

name  of  the  material  unless  a  local  section  notation  is  in  use. 
Except  for  a  few  cases  where  it  is  desirable  to  distinguish  between 
the  metals  in  adjacent  parts,  such  as  the  babbit  and  the  casting 
of  a  bearing,  nothing  is  gained  by  using  characteristic  section 
lines  since,  in  general,  a  note  must  be  added  to  insure  proper 
interpretation.  Fig.  258  shows  a  few  sections  in  common  use. 

Breaks.    Where  it  is  desirable  to  omit  part  of  a  shaft  or  rod, 
either  may  be  broken  and  the  break  indicated  as  shown  in  Fig. 


230 


MECHANICAL  DRAWING 


FIG.  257.    SECTION  THROUGH  RIBS,  SHAFTS,  BOLTS,  ETC. 


CAST   IRON  CAST  STEEL  WROUGHT    IRON  BRASS 


BRICK 


CONCRETE 


LEATHER 


WOOD 


FIG.  258.    CONVENTIONAL  CROSS-SECTIONING 


ADVANCED  DRAWING 


231 


259.    The  ragged  line  representing  the  break  is  drawn  freehand 
in  both  the  pencil  and  the  ink  drawing. 


f?ecfangv/ar  Gar 


ftecfangu/ar  Sec  f ton  -Weed 


found 


or  Ho/Jovr  Shaft 


I  Bean?  Channef  Ang/e 

FIG.  259.    CONVENTIONAL  BREAKS 


Z-Bar 


Wood  Screws  are  made  of  steel  or  brass.  They  have  heads  of 
various  shapes  as  shown  in  Fig.  260.  The  size  of  screws  is  given 
in  terms  of  their  number  and  their  length,  which  is  indicated  by 
giving  the  gage  number.  The  threads  of  wood  screws  are  repre- 
sented conventionally  as  shown  in  Fig.  260. 

Furniture  and  Cabinet  Details.  Various  joints  and  a  few 
other  common  constructions  used  in  furniture  and  cabinet  con- 
struction are  shown  in  Figs.  261  and  262. 


FIG.  260.     CONVENTIONAL  EEPRESENTATION  OF  WOOD  SCREWS 


FURNITURE  AND  CABINET  PROBLEMS 
PEEPAEATOEY  INSTEUCTIONS  FOE  DEAWING  PLATE  35 

The  problems  for  this  plate  were  selected  with  the  idea  of 
giving  practice  in  drawing  and  dimensioning  projects  in  furni- 
ture making  and  also  to  set  before  the  student  typical  examples 


232 


MECHANICAL  DRAWING 


6/uec/  anct  Stocked 
FIG.  261.    JOINTS 


Dade  and  ffabbef 


Dado.  Tongue  t 


ftav/iched  M0rf/se  ar?d  Tenor? 


FIG.  262.    JOINTS 


(233) 


-<^M 


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te-2  - 


I      -     II  II 


XJ 


1 


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T 


3D 


Ld 
CQ 

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cO 

u 

Q 


^Drawer  6 'vide, 


_J  2"L_    Section  on  MN 


Qefa/1  of  Drawer 


MIL 


(236) 


FIG.  265.    MACHINE  SHOP  BENCH 


ADVANCED  DRAWING 


237 


u  1 

M      H> 

'Oetet/of  Joint  at  B 


PIG.  266.    PHONE  TABLE  AND  CHAIR 


238 


MECHANICAL  DRAWING 


BILL:  OF  STOCK                 ] 

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PCS 

"SIZE 

NAME 

MATERIAL 

M".FT. 

FE.R.FT 

TOTAL 

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FIG.   2G7.     LIBRARY  TABLE 


ADVANCED  DRAWING 


239 


of  furniture  construction.  In  order  to  cover  this  field  as  thor- 
oughly as  possible,  two  type  problems  of  widely  different  char- 
acter are  presented.  Figs.  263  and  264.  The  student  should  fix 


Crossbcu 


Minge  Joftrf  of  BacA 


Defy// ef  Jo/nf  af  A        Section  of  front 


jil/y/hf  and  Corner  at  Q 


FIG.  268.    MORRIS  CHAIR 


in  mind  the  correct  proportion  of  the  joints  used  in  these  prob- 
lems as  well  as  their  names  and  uses  by  referring  to  the  discussion 
and  figures  on  pages  231,  232,  and  233. 


240  MECHANICAL  DRAWING 

DATA  FOR  DRAWING  PLATE  35 

Given:  The  perspective  sketch  of  the  object  shown  in  Fig 
265,  266,  267,  or  268. 

Required:  To  draw  the  orthographic  views  of  the  object 
shown  in  Fig.  265,  266,  267,  or  268,  or  any  similar  problem  as 
assigned  by  the  instructor. 


3° 

~  Groove        R  in  finished  face, 


ll  for  •    Split  Cotter.   1914-15= 


=  A//  Fillets  j.  R  Unless  Otherwise^ 
~  Specified  Key  for  9"  Spur  Gear:: 
-  lxQ  Stud  Bolt  Nut,  1915-16= 


FIG.  269.    LETTERING  PLATE  35 

The  problems  for  this  plate  are  designed  to  give  practice  in 
making  working  drawings  for  various  kinds  of  cabinet  work  and 
to  familiarize  the  student  with  typical  cabinet  construction. 

DATA  FOR  LETTERING  PLATE  35 

Given:     Plate  35  to  reduced  size.    Fig.  269. 
Required:     To  make  the  plate  to  an  enlarged  scale. 

DATA  FOR  DRAWING  PLATE  36 

Given:     The  pencil  mechanical  drawing,  Plate  35. 
Required :     To  make  a  tracing  of  Plate  35. 


ADVANCED  DRAWING  241 

DATA  FCR  LETTERING-  PLATE  36 

Given:     Plate  36  to  reduced  size.     Fig.  270. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


-  Moke  Oil  Tight    Drill  for  No,  I6~ 

~  Standard  Flat  Head  Machine 

I" 
z  Screw,     3<?    Lock  Nut   Washer     z 

z  These  Holes  in  Piece  No,   64181,  z 
~On/y     Drawing  No,    166,     Piece  z 


FIG.  270.    LETTERING  PLATE  36 


DATA  FOE  DRAWING  PLATE  37 

Given:  The  orthographic  views  of  the  objects  shown  in 
Fig.  273,  274,  275,  or  276. 

Required:  To  draw  to  large  scale  two  views  of  objects 
shown  in  Fig.  273,  274,  275,  or  276,  with  sections  and  details  of 
joints  and  paneling;  or  any  similar  problem  assigned  by  the 
instructor. 


it 

Xi 

§1 

II 


% 


-./• 


.U 


~\      r 

\      \ 
\      ( 
\ 

n 

n 

\      \ 

\ 

\ 

\ 

\ 

\       \ 
\       t 
\        ! 

\ 
\   \ 

1 


244 


MECHANICAL  DRAWING 


FIG.  273.     GLUE  BENCH 


F.IG.  274.    CABINET  FOR  DRAWING  EOOM 


f-J 


m 


FIG.  275.    CABINET  FOR  CLOT 

1             V>     I 

HES  PRESS          U  /3~  —  +• 

,  >             t± 

•r  T-|lrT—  *'  f  •  -11  :  -    + 

a- 

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4                  4 

4 

4 

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i 

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c 

(1 
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4-                                       4- 

4-                                4- 

4-                                      4- 

4-                                     4- 

<  2~/l  "  •>• 

i-^'rfd 

1       •»!•! 

FIG.  276.    CHIFFONIER 


246  MECHANICAL  DRAWING 


DATA  FOR  LETTERING  PLATE  37 

Given:    Plate  37  to  reduced  size.    Fig.  277. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


~  Round  Point  Set'  Screw  -Brass=L 

r 

~l  Required      Top  2      Special    ~ 


Threads  per  I"         Bottom 
Spring  Plate   Brass  -Finish  -/ 
Required,    Outside  Finish  All  Over 


FIG.  277.    LETTERING  PLATE  37 


DATA  TOR  DRAWING  PLATE  38 

Given :     The  pencil  mechanical  drawing  for  Plate  37. 
Required:     To  make  a  tracing  of  Plate  37. 


DATA  FOR  LETTERING  PLATE  38 

Given:     Plate  38  to  reduced  size.    Fig.  278. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


ADVANCED  DRAWING  247 


MACHINE  DRAWING 

A  Bill  of  Material  may  be  given  on  the  drawing  or  on  a  sep- 
arate sheet.  It  is  a  tabulated  form  in  which  such  information  as 
the  following  is  given : 

1.  Number  of  each  part  required  on  one  complete  machine 
or  structure. 


z    A  careful  study  of  the  form 
proportion  of  each  letter 
be  made  before  the  stu-  z 
can  hope  TO  make  any  conE. 
^siderable  progress  in  lettering 


FIG.  278.    LETTERING  PLATE  38 

2.  Description  or  name  of  piece. 

3.  Mark  or  number  by  which  a  piece  is  designated  on  the 
drawing. 

4.  General  drawing  number. 

5.  Shop  drawing  number. 

6.  Erection  drawing  number. 

7.  Material  from  which  each  piece  is  made. 

8.  Pattern  number  if  cast. 

9.  Where  used. 

10.  Estimated  weight. 

11.  Order  number. 


248 


MECHANICAL  DRAWING 


,    Y    _       ^  ^  Y 

i 

~/" 

-p 

4 

9  " 

<  —  j2    —  >• 

\ 

• 

tr 

Swing  Arm 

-h 

CJ. 

1 

1 

5 

Shie/d  P/ate    . 

1 

W.I, 

4 

Feed  Lever  Latch  Pin 

I 

W.I. 

3 

Reach  ftcd 

/ 

W.I. 

2 

Thumb  Latch 

1 

C.I. 

1 

Feed  Lever 

/ 

C.I. 

DETAILS 

FOR 
OHIO  MONARCH  SHREDDER 

34    |     359    |    A.6.S. 

SCALE-HALF  SIZE 

FIG.  279.     BILL  OF  MATERIAL 


FIG.  280.    CONSTRUCTION  OF  THE  HELIX 


The  bill  of  material  includes  standard  parts  such  as  bolts  and 
screws  which  are  not  detailed  on  the  drawings.  A  simple  bill  of 
material  is  shown  in  Fig.  279. 


ADVANCED  DRAWING 


249 


$crcw  Threads.  The  curve  of  the  screw  thread  is  the  helix. 
It  is  generated  by  a  point  which  moves  on  the  surface  of  a  cylin- 
der and  which  advances  uniformly  in  the  direction  of  the  axis  of 
the  cylinder  and  at  the  same  time  has  a  uniform  motion  around 


US.  STANDARD 


SQUARE 


ACME. 


60°-y  Taper^ "per  inch  of  /e firth 


•« —    4-  Threads 
/mperfecf 


/?  Threads 
Ft///af  roof 


t .8  outside  d/am.  -t-4.8  

Number  of  threads  per  inch 

Compete  threads -F/at  tops  —Sharp  bottoms 


BRIGGS    STANDARD  PIPE  THREADS  -MODIFIED 

FIG.  281.    PROPORTION  OF  COMMON  THREAD  FORMS 


its  axis.  Fig.  280  shows  the  construction  for  the  helix.  The  dis- 
tance in  the  direction  of  the  axis  traversed  by  a  point  in  one  revo- 
lution is  called  the  pitch.  Pitch  in  the  case  of  a  thread  is  its 
advance  in  the  direction  of  the  axis  in  one  revolution. 

In  Fig.  281  the  proportions  of  the  several  common  thread 
forms  are  shown  to  a  large  scale. 


250 


MECHANICAL  DRAWING 


The  V-thread  is  shown  in  Fig.  282  as  it  would  actually  appear 
with  the  edges  drawn  as  helices.  On  account  of  the  difficulty  of 
constructing  and  drawing  these  curves  they  are  usually  conven- 


FIG.  282.    V-THREAD,  SHOWING  HELICES 


tionalized  into  straight  lines  as  shown  in  Fig.  283.  The  method 
commonly  used  for  representing  screws  up  to  about  one  inch  in 
diameter,  as  measured  on  the  drawing,  is  still  further  simplified 
by  omitting  the  short  inclined  lines  forming  the  "saw  teeth." 


ADVANCED  DRAWING 


251 


Fig.  284.  On  the  pencil  drawing  no  distinction  is  made  in  the 
weight  of  the  two  sets  of  parallel  lines  drawn  across  the  screw, 
but  on  the  tracing  it  is  customary  to  make  a  striking  contrast 
between  the  longer  and  shorter  lines  as  shown. 


FIG.  283.    V-THREAD.    CONVENTIONAL  EEPRESENTATION  FOR  LARGE  SIZES 


In  this  course  the  shorter  lines  will  be  made  object-line  width 
and  the  longer  lines  center-line  width.  The  angle  at  which  these 
lines  are  drawn  is  estimated.  It  remains  practically  constant  for 
all  sizes  of  standard  screws  as  the  pitch  of  the  thread  increases 
with  the  diameter  of  the  screw.  It  will  be  noted  that  the  lines  in 
the  section  view  of  the  nut  make  the  opposite  angle  to  the  hori- 
zontal that  those  on  the  screw  make  because  of  the  fact  that  the 


252 


MECHANICAL  DRAWING 


part  of  the  nut  shown  matches  the  invisible  half  of  the  screw.  The 
lines  are  usually  spaced  by  eye.  Guide  lines  should  be  drawn  to 
limit  the  length  of  the  shorter  lines. 

In  the  conventional  end  view  of  the  bolt,  the  circle  represent- 
ing the  outer  edges  of  the  thread  is  a  full  line,  while  one-half  of 
the  circle  representing  the  inner  edges  of  the  thread  is  a  dotted 
line  and  the  other  half  is  a  full  line. 


FIG,  284,     V-THREAD.     CONVENTIONAL  REPRESENTATION   FOR  SMALL   SIZES 


In  the  conventional  end  view  of  the  nut,  the  circle  represent- 
ing the  inner  edges  of  thread  is  a  full  line,  while  one-half  of  the 
circle  representing  the  outer  edges  of  the  thread  is  a  dotted  line 
and  the  other  half  is  a  full  line. 

A  study  of  the  relation  of  these  conventions  to  the  form  of 
the  object  should  enable  the  student  to  fix  in  mind  the  principles 
on  which  they  are  based.  With  this  relation  in  mind  it  will  be 
unnecessary  for  him  to  refer  to  the  figures  in  rendering  the 
convention. 

The  United  States  Standard  (U.  S.  S.)  or  Sellers  thread, 
Fig.  281,  differs  from  the  sharp  V-thread  in  that  the  outer  and 
inner  edges  of  the  thread  are  flattened.  The  same  convention 
is  used  for  representing  it  that  is  used  for  the  sharp  V-thread. 


ADVANCED  DRAWING 


253 


The  Square  Thread  is  shown  in  Fig.  285  with  the  edges  drawn 
as  helices.  Fig.  286  is  a  conventional  representation  of  the  screw 
and  nut  in  which  the  helices  have  been  replaced  by  straight  lines. 


FIG.  285.    SQUARE  THREAD.    EDGES  DRAWN  AS  HELICES 


For  small  sizes,  the'  method  shown  in  Fig.  287  is  generally 
used  because  of  its  simplicity.  The  Acme  screw  thread  is  rep- 
resented conventionally  as  shown  in  Fig.  288.  It  is  convenient 
in  drawing  to  make  the  angle  between  the  faces  of  the  thread 
30°  instead  of  29°. 


FIG.  286.    SQUARE  THREAD.    CONVENTIONAL  EEPRESENTATION  FOR  LARGE 

SIZES 


FIG.    287.      SQUARE    THREAD.     CONVEN- 
TIONAL REPRESENTATION  FOR  SMALL  SIZES 

(254) 


FIG.  288.    ACME  THREAD.   CON- 
VENTIONAL EEPRESENTATION 


ADVANCED  DRAWING 


255 


Pipe  Thread.  The  basic  form  of  the  Briggs  standard  pipe 
thread  is  that  of  the  V- thread.  This  thread  is 'rounded  slightly 
at  the  outer  and  inner  edges.  A  modified  form  in  which  the 
threads  have  flat  outer  edges  and  sharp  inner  edges  is  shown  in 
Fig.  289.  This  form  is  used  by  manufacturers  because  of  the 
comparative  ease  with  which  taps  and  dies  are  made  for  cutting 
the  threads. 


FIG.  289.    PIPE  THREADS.    CONVENTIONAL  REPRESENTATION 


The  threaded  portion  of  the  pipe  tapers  one  thirty-second 
of  an  inch  in  radius  for  each  inch  of  length. 

Pipe  threads  are  represented  conventionally  as  shown  in 
Fig.  289. 

Springs.  The  curve  of  the  coil  spring  is  the  helix.  Fig.  290 
shows  a  spring  in  which  the  curves  are  drawn  and  also  the 
conventional  representation  which  shows  the  curves  replaced  by 
straight  lines. 

Bolts  and  Nuts.  A  bolt  consists  of  a  rod  with  a  head  on  one 
end  and  a  screw  on  the  other  to  receive  a  nut.  Fig.  291.  What 
are  known  as  United  States  Standard  bolts  and  nuts  are  shown 


256 


MECHANICAL  DRAWING 


in  Figs.  292  and  294.  The  proportions  given  by  the  formulae  are 
those  adopted  for  rough  bolts  and  nuts.  The  finished  nuts  are 
3JV  less  in  width  and  thickness  than  the  rough  nuts.  The  fin- 


FIG.  290.    COIL  SPRING  SHOWING  ACTUAL  AND  CONVENTIONAL 
REPRESENTATION 


BOLT  CAP  5CBEW  STUD  STUD    BOLT 

FIG.  291.    COMMON  SCREW  FASTENINGS 


ished  heads  have  the  same  sizes  as  the  finished  nuts.  A  table  of 
standard  sizes  may  be  found  in  an  engineering  handbook. 
United  States  Standard  threads  are  used  on  these  bolts. 


h-vH 


FIG.  292.  ACTUAL  PROPORTIONS. 
HEXAGONAL  HEAD — U.  S.  STANDARD 
BOLTS  AND  NUTS 


FIG.  293.  CONVENTIONAL  REPRE* 
SENTATION.  HEXAGONAL  HEAD — U. 
S.  STANDARD  BOLTS  AND  NUTS 


FIG.  294.     ACTUAL  PROPORTIONS.  FIG.  295.     CONVENTIONAL  REPRE- 

SQUARE     HEAD — U.     S.     STANDARD          SENTATION.     SQUARE    HEAD — U.    S. 

BOLTS  AND  NUTS  STANDARD  BoLts  AND  NUTS 

(257) 


258  MECHANICAL  DRAWING 

Figs.  293  and  295  show  the  conventional  methods  of  repre- 
senting hexagonal  and  square  bolt,  heads  and  nuts.  Hexagonal 
heads  and  nuts  are  usually  drawn  to  show  three  faces,  whereas 
square  heads  and  nuts  are  drawn  to  show  two  faces.  When  this 
is  done  the  hexagonal  forms  are  easily  distinguished  from  the 
square  forms. 

Since  the  proportions  of  the  head  and  nut  of  standard  bolts 
are  fixed,  it  is  only  necessary  to  give  three  dimensions,  viz.,  the 
length  of  the  bolt  under  the  head,  the  length  of  the  threaded 
portion,  and  the  diameter. 

A  Stud  is  a  rod  threaded  at  both  ends.  One  end  is  screwed 
into  a  threaded  hole.  The  other  end  receives  a  nut.  In  Fig.  291 
a  standard  nut  is  used. 

A  stud  placed  through  two  unthreaded  holes  with  a  nut  at 
each  end  is  called  a  stud  bolt.  Fig.  291. 

Cap  Screws  are  similar  in  form  to  bolts.  They  hold  two 
parts  together  by  passing  through  an  unthreaded  hole  in  one 
and  a  threaded  hole  in  the  other.  Fig.  291.  Heads  of  various 
forms  are  used  as  shown  in  Fig.  296. 

Machine  Screws  are  similar  to  cap  screws  in  form.  They 
differ  from  them  by  being  measured  in  decimals  instead  of  even 
fractions  of  an  inch. 

Tap  Bolts  have  the  same  form  as  cap  screws  except  that  they 
are  not  finished  before  threading,  are  threaded  for  their  full 
length,  and  are  used  for  rough  work. 

Set  Screws  are  used  ordinarily  to  prevent  relative  motion  of 
two  parts  such  as  a  pulley  and  shaft.  The  screw  is  passed 
through  a  threaded  hole  in  one  part  and  the  point  is  forced 
against  another  part.  The  proportions  of  the  set  screws  and  the 
shapes  of  the  different  points  are  shown  in  Fig.  297. 

Multiple  Threads.  It  is  sometimes  necessary  to  increase  the 
distance  traversed  by  a  nut  in  one  revolution.  If  a  coarse 
enough  single  thread  is  used  to  give  the  advance  required,  the 
strength  of  the  bolt  may  be  considerably  diminished.  To  obviate 
this  difficulty,  more  than  one  thread  may  be  cut  side  by  side, 
The  advance  for  one  revolution  of  a  multiple  thread  is  commonly 
called  the  "lead,"  and  the  pitch  is  the  distance  between  corre- 
sponding points  on  two  successive  threads.  Figr.  298.  The  con- 


FLAT   FILLISTER  OVAL  FILLISTER 


FLAT  COUNTERSUNK       OVAL  COUNTERSUNK 


BUTTON 


o 

END  FOR  ALL 


i 

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A: 


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u 


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,032 
.040 
,064 
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133 
,133 


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FIG.  296.    VARIOUS  FORMS  OF  CAP  SCREW  HEADS 


(259) 


260 


MECHANICAL  DRAWING 


ventions  for  multiple  threads  are  distinguished  from  those  for 
single    threads    by    increasing    the    angle    of    the    cross    lines 


.      cf'O/a at  bottom. 
-L  of  rfiread. 


Regular      tewHead    Necked       Head/us          Cup         HatfifOf  Round  Pivof 

FIG.  297.    SET  SCREW  HEADS  AND  POINTS 


Single  L.H. 


Sing/eftrt         !  Double  FtH      *      Doubfe  RH.          Single  U* 

FIG.  298.    CONVENTIONAL  REPRESENTATION  OF  MULTIPLE  THREADS 

and  by  a  note  indicating  the  kind  of  threads  as  double,  triple, 
quadruple,  etc. 


ADVANCED  DRAWING 


261 


Methods  of  Indicating  Finish.  Where  and  how  a  part  is  to 
be  finished  may  be  shown  by  symbols  or  notes,  or  both.  In  case 
a  hole  is  to  be  bored,  drilled,  reamed,  cored,  etc.,  a  note  is  usually 
made  in  connection  with  the  dimension  figure.  Fig.  299.  A 
cylindrical  surface  to  be  turned,  ground,  polished,  rough  finished, 
etc.,  may  have  the  method  of  finishing  indicated  in  the  same  way. 
In  case  all  surfaces  of  the  object  are  to  be  finished  and  the  method 
can  be  left  to  the  workman's  judgment,  a  note  may  be  made: 
FINISH  ALL  OVER.  Where  only  certain  surfaces  are  to  be  finished, 


FIG.  299.    METHODS  OF  INDICATING  FINISH 

the  character  f  may  be  placed  across  the  lines  which  represent 
these  surfaces  viewed  edgewise.    Fig.  299. 

While  the  indication  of  finish  is  a  very  small  part  of  a  draw- 
ing, it  is  nevertheless  a  very  important  detail.  The  omission  of  a 
finish  mark  may  mean  the  making  of  a  large  number  of  castings 
from  a  pattern  on  which  no  stock  has  been  allowed  for  finish. 

SKETCHING  FROM  THE  OBJECT 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  39 

Freehand  sketches  may  be  made  by  a  designer  to  get  an  idea 
of  the  form  of  certain  parts  in  working  out  his  design.  A 
designer  or  chief  draftsman  may  use  them  as  a  means  of  con- 
veying his  ideas  to  a  junior  draftsman. 


262  MECHANICAL  DRAWING 

In  case  a  machine  is  broken,  time  may  often  be  saved  by 
sketching  the  broken  parts  in  the  shop  and  having  parts  made 
to  replace  them  instead  of  sending  to  the  manufacturer  of  the 
machine  for  repairs.  When  a  change  of  design  is  contemplated 
and  the  original  drawings  are  not  to  be  had,  sketches  of  the 
parts  affected  may  be  made  from  the  existing  machine  and  the 
desired  changes  incorporated  in  the  mechanical  drawing  made 
from  sketches.  When  time  permits  and  it  is  desirable  to  have 
.a  permanent  record  of  the  drawing  a  mechanical  drawing  should 
Jbe  made  from  the  sketch,  but  in  an  emergency  the  sketch,  if 
carefully  drawn  and  checked,  may  be  used  as  a  shop  drawing. 

In  making  the  orthographic  sketches  of  Chapter  II,  the  fact 
that  certain  views  of  the  object  were  shown  in  correct  proportion 
and  were  dimensioned  made  the  task  of  drawing  the  other  views 
of  the  object  to  larger  scale  a  simple  process. 

The  drawing  of  orthographic  sketches  from  dimensioned  per- 
spective sketches,  Chapter  III,  increased  the  difficulty  of  selecting 
and  arranging  the  views,  and  to  some  extent,  the  dimensions. 

Compared  to  sketching  from  orthographic  and  perspective 
views  the  average  beginner  will  find  the  making  of  an  ortho- 
graphic sketch  from  the  object  a  rather  intangible  problem.  He 
will  find  it  difficult  to  represent  in  outline  an  object  which  to  the 
eye  stands  out  in  relief  in  light  and  shadow.  At  the  same  time 
he  must  keep  in  mind  the  fact  that  only  two  dimensions  can  be 
represented  in  each  view.  He  is,  also,  confronted  with  the  neces- 
sity of  establishing  center  lines,  datum  lines,  etc.,  which  are  not 
edges  of  the  object  but  are  of  prime  importance  in  the  drawing. 

He  must  select  dimensions  to  show  the  proper  relation  between 
the  details  of  the  object.  These  dimensions  must  also  be  selected 
to  show  similar  distances  on  parts  which  are  fitted  to  the  object. 
He  must  use  his  judgment  as  to  the  accuracy  with  which  each 
measurement  should  be  made,  as  to  the  allowance  for  inaccuracies 
of  workmanship,  inaccuracies  inherent  in  the  process  of  manu- 
facture, etc. 

Selecting  Views.  In  selecting  the  views  of  an  object  to  be 
drawn,  the  principles  developed  in  previous  chapters  should  be 
used.  In  general  only  necessary  views  are  drawn,  but  in  the 
sketch  additional  views,  partial  views,  sections,  etc.,  may  be 


ADVANCED  DRAWING  263 

drawn  in  preference  to  complicating  the  necessary  views  with 
lines. 

Methods  Used  in  Drawing.  After  an  inspection  of  the  object 
and  after  a  decision  has  been  reached  as  to  what  views  are  to  be 
drawn,  the  student  should  place  the  object,  if  it  is  removable,  so 
that  he  can  obtain  the  required  views  without  changing  its  posi- 
tion. Very  often  the  shifting  of  the  object  leads  to  errors  in  the 
relative  position  of  the  views,  such  as  placing  the  left  side  view 
to  the  right  instead  of  to  the  left  of  the  front  view.  With  the 
object  always  in  the  same  position  and  the  principles  as  to  rela- 
tion of  views,  developed  in  former  chapters,  well  in  mind,  such 
errors  are  not  likely  to  occur.  The  views  should  show  the  object 
in  as  good  proportion  as  can  be  obtained  without  scaling  it.  Time 
should  not  be  wasted  in  taking  dimensions  at  this  stage  arid 
attempting  to  lay  them  out  to  scale. 

The  first  step  in  the  construction  of  the  drawing  is  to  locate 
center  or  other  reference  lines.  Circles  should  be  constructed  by 
first  drawing  two  center  lines  at  right  angles.  The  radii  should 
then  be  estimated  from  the  intersection  on  these  lines,  and  the 
circle  drawn  through  the  four  points  located. 

If  the  object  is  of  cylindrical  form,  it  will  usually  be  found 
advantageous  to  draw  the  circular  view  first  because  of  the  ease 
with  which  the  other  views  may  be  drawn  by  projecting  the 
diameters  from  the  circular  view.  In  some  cases  where  the  views 
of  the  details  of  the  object  are  interdependent,  it  will  be  necessary 
to  construct  two  or  more  views  simultaneously. 

The  use  of  the  coordinate  paper  greatly  facilitates  the  align- 
ment and  proportioning  of  the  details  in  different  views.  The 
student  should  learn  to  use  the  ruled  lines  merely  as  a  guide 
in  locating  and  proportioning  the  views.  The  use  of  the  squares 
as  units  of  measurement  for  the  purpose  of  drawing  the  object 
to  scale  is  not  to  be  considered ;  for  while  it  is  admitted  that  their 
use  will  aid  in  proportioning  the  drawing,  it  is  not  one  of  the 
functions  of  a  freehand  sketch  to  show  the  object  in  accurate  pro- 
portion, and  the  counting  of  the  squares  entails  a  serious  waste  "of 
time. 

Selection  and  Arrangement  of  Dimensions.  When  the  views 
of  the  object  are  compete  and  have  been  checked  carefully  to 


264  MECHANICAL  DRAWING 

make  sure  that  they,  together  with  necessary  supplementary 
notes,  fully  represent  the  object,  the  question  of  dimensioning 
should  next  be  considered. 

To  dimension  an  object  properly  the  draftsman  must  have 
some  knowledge  of  the  process  through  which  it  must  go  in  the 
shop  to  become  a  finished  product.  If  it  be  a  casting  he  must 
know  what  dimensions  the  patternmakers  will  use  in  making  the 
pattern  ?  if  it  has  finished  surfaces  he  must  know  with  what 
machines  each  is  finished  and  give  the  dimensions  in  such  a  way 
that  the  machinist  may  use  them  directly.  Example :  The  diam- 
eter of  a  part  to  be  turned  in  the  lathe  should  be  given  rather 
than  the  radius,  since  the  most  convenient  and  accurate  method 
of  measuring  a  cylindrical  surface  is  by  means  of  the  caliper  or 
micrometer. 

Enough  dimensions  should  be  given  to  determine  completely 
the  sizes  and  relation  of  the  details  of  the  object.  When  a  sketch 
is  made  at  some  distance  from  the  place  at  which  it  is  to  be  used 
either  to  furnish  information  for  a  mechanical  drawing  or  as  a 
shop  drawing,  the  draftsman  must  be  sure  that  all  necessary  di- 
mensions are  given.  However,  he  should  guard  against  giving  un- 
necessary or  useless  dimensions  in  an  attempt  to  avoid  omitting 
necessary  dimensions.  All  finished  surfaces,  special  fits,  etc., 
should  be  marked  in  such  a  way  that  they  cannot  be  misunder- 
stood. The  nature  of  the  sketch  admits  of  a  freer  use  of  explan- 
atory notes  than  would  be  tolerated  on  the  mechanical  drawing. 

Details  which  are  required  to  be  accurately  located  on  the 
object  should  be  referred  by  dimensions  to  center  lines  or  finished 
surfaces.  As  the  dimensions  to  be  given  are  planned,  the  exten- 
sion and  dimension  lines  should  be  drawn,  but  the  dimension 
figures  should  not  be  inserted  until  all  such  lines  are  drawn. 

When  the  extension  and  dimension  lines  are  drawn  the  arrow- 
heads should  be  made. 


MEASUREMENTS 


265 


MEASUREMENTS 
MEASURING  INSTRUMENTS 

The  following  paragraphs  contain  a  short  description  of  the 
more  common  tools  used  in  taking  measurements  from  the  object 
for  the  purpose  of  dimensioning  a  sketch. 

The  Folding  Rule.  Rules  are  made  of  various  lengths  which 
may  be  folded  and  carried  in  the  pocket.  The  smallest  divisions 
are  usually  -j^"  and  TV'.  Their  construction  makes  the  division 
into  smaller  fractions  of  an  inch  unwarrantable  as  these  rules 
cannot  be  depended  upon  to  read  accurately  to  smaller  units. 


FIG.  300.    FOLDING  RULE 


A  two-foot  rule  will  be  found  very  serviceable  where  accuracy  is 
not  required.  While  convenient  in  measuring  long  distances, 
they  are  in  general  suitable  only  for  rough  work.  Fig.  300. 

The  Steel  Tape.  SteeJ  tape  may  be  had  in  lengths  of  3  feet  to 
200  feet  or  more.  As  in  the  case  of  the  rules,  their  divisions  are 
coarse  and  cannot  be  used  for  accurate  measurements.  Fig.  301. 

The  Steel  Scale.  For  accurate  measurements  steel  scales  are 
used.  These  scales  may  be  had  in  lengths  of  1"  to  72",  and  with 
various  combinations  of  graduations  on  the  two  edges  of  each 
side.  The  most  common  graduations  are  J",  ^",  3*5",  ST"»  an^ 
Tfo".  Fig.  302. 

The  Adjustable  Square.  Fig.  302  shows  a  square  in  which 
the  blade  is  adjustable  in  the  stock.  The  blade  is  an  ordinary 


266 


MECHANICAL  DRAWING 


steel  scale  with  a  groove  made  to  receive  a  hook  which  serves  to 
clamp  the  blade  in  the  stock.  The  stock  is  furnished  with  a  level. 
This  instrument  will  be  found  useful  in  many  ways. 


FIG.  301.    STEEL  TAPE 


u  '  01 


FIG.  302.    ADJUSTABLE  SQUARE 


Calipers.  Calipers  are  used  for  obtaining  measurements  of 
length  or  diameter  where  the  scale  cannot  be  applied  directly. 
After  they  are  set  to  the  distance  which  is  to  be  measured  they 
are  placed  upon  a  scale  and  the  distance  read.  Fig.  303  shows 
two  forms  of  calipers,  one  adapted  to  outside  measurements,  such 
as  diameters  of  shafts,  etc.,  while  the  other  is  best  suited  to  inside 
measurements,  such  as  the  diameter  of  holes. 

Other  Devices,  such  as  the  plumb  bob,  straightedge,  and  sur- 
face gauge,  may  be  of  occasional  use  in  taking  measurements 
from  the  object. 


MEASUREMENTS  267 

TAKING  MEASUREMENTS 

Having  drawn  the  dimension  lines,  extension  lines,  and  arrow- 
heads, there  remain  the  taking  of  dimensions  from  the  object  and 
inserting  them  on  the  drawing.  In  doing  this,  judgment  must  be 
exercised  in  determining  with  what  degree  of  accuracy  each 
measurement  should  be  taken.  Examples:  Dimensions  between 
rough  surfaces  usually  need  not  be  given  closer  than  the  nearest 
•jV  or  3*2",  while  the  inside  diameter  of  the  bushing  in  which  a 


FIG.  303.    INSIDE  CALIPER.    OUTSIDE  CALIPEB 

shaft  is  to  run  would  probably  be  given  .003"  or  .004"  larger 
than  the  diameter  of  the  shaft. 

Judgment  must  also  be  exercised  in  determining  whether 
irregularities  such  as  the  uneven  thickness  of  castings,  lack  of 
symmetry,  apparent  discrepancies  in  spacing  of  holes,  etc.,  are 
intentional  and  essential  to  the  design  and  construction  of  the 
object,  or  whether  they  are  non-essentials  which  have  come  about 
through  natural  causes  in  the  process  of  manufacture  or  poor 
workmanship,  and  should  be  eliminated  from  the  drawing. 

The  problems  arising  in  the  taking  of  measurements  from  the 
object  are  so  varied  that  no  attempt  will  be  made  here  to  discuss 
the  subject  fully.  However,  a  few  examples  may  be  given  which 
will  illustrate  the  use  of  the  measuring  instruments  and  also  the 
general  principles  involved  in  securing  dimensions. 


268 


MECHANICAL  DRAWING 


The  distance  between  points  on  the  same  plane  surface  such 
as  the  distance  between  two  parallel  edges  of  the  surface  and  the 


FIG.  304.    MEASURING  A  LINEAR  DISTANCE  WITH  THE  SCALE 


FIG.  305.    MEASURING  A  LINEAR  DISTANCE  WITH  THE  SQUARE 

length  of  cylinders  may  be  measured  directly  with  the  rule  or 
steel  scale,  as  shown  in  Fig.  304.    This  method  is  only  applicable 


MEASUREMENTS 


269 


for  accurate  measurement  when  the  corners  are  sharp.  When 
the  corners  are  rounded,  the  same  dimension  may  be  obtained  by 
using  the  square  or  caliper,  as  shown  in  Fig.  305  or  306. 


FIG.  306.    MEASURING  A  LINEAR  DISTANCE  WITH  THE  CALIPER 


FIG.  307.    READING  THE  CALIPER  MEASUREMENT  FROM  THE  SCALE 

The  use  of  the  square  here  needs  no  explanation.  The  caliper 
must  be  set  very  carefully  so  that  its  points  touch  both  surfaces 
between  which  the  distance  is  to  be  measured,  but  not  with 


270 


MECHANICAL  DRAWING 


enough  pressure  to  spring  the  caliper.  The  proper  adjustment  is 
obtained  by  means  of  the  thumb  screw  on  the  adjustable  caliper 
or  by  tapping  the  leg  against  a  solid  object  in  the  case  of  the 
plain  caliper.  The  distance  between  the  points  of  the  caliper  is 


FIG.  308.    MEASURING  THE  DIAMETER  OF  A  CYLINDER  WITH  THE  CALIPER 

measured  with  the  steel  scale,  as  shown  in  Fig.  307.  Note  that 
one  point  of  the  caliper  rests  against  the  end  of  the  scale  so  that 
the  operator's  attention  may  be  given  entirely  to  reading  the 
scale  division  at  the  other  point 


FIG.  309.    MEASURING  THE  DIAMETER  OF  A  HOLE  WITH  THE  CALIPER 

The  outside  caliper  is  used  in  obtaining  dimensions  of  curved 
surfaces.  See  Fig.  308.  It  is  adjusted  and  the  measurement 
taken  from  the  scale  as  previously  described. 

The  inside  caliper  is  used  in  measuring  the  diameters  of  holes 
and  the  openings  between  surfaces  where  the  scale  cannot  be 
applied.  Fig.  309.  Measurements  are  obtained  from  the  inside 


MEASUREMENTS 


271 


caliper  by  placing  it  over  the  scale,  as  shown  in  Fig.  310.    Note 
that  the  scale  is  placed  against  a  smooth  surface  and  at  right 


FIG.  310.    BEADING  MEASUREMENTS  FROM  THE  INSIDE  CALIPER 


FIG.  311.     MEASURING  THE  CENTER  TO  CENTER  DISTANCE  OF  EQUAL  HOLES 

angles  to  it.  One  point  of  the  inside  caliper  is  placed  against  the 
smooth  surface.  By  this  method  the  scale  division  opposite  the 
other  point  may  be  easily  and  accurately  read. 


272 


MECHANICAL  DRAWING 


When,  as  is  very  often  the  case,  it  is  necessary  to  locate 
centers  of  holes  with  reference  to  each  other  or  with  reference  to 
some  finished  surface  or  datum  line,  a  difficulty  arises  from  the 


l&fit 


Utl-'t  u!//'f-R 


m 


FIG.  312.    TYPE  PROBLEM.    CYLINDER  HEAD.    FREEHAND  SKETCH 


fact  that  a  center  line  does  not  exist  on  the  object  and  must  be 
established  or  the  dimension  obtained  in  a  roundabout  way. 

In  the  case  of  two  holes  of  equal  diameter,  the  center-to-center 
distance  may  be  obtained  by  measuring  from  the  near  edge  of 
one  to  the  far  edge  of  the  other.  Fig.  311.  The  center-to-center 
distance  of  holes  of  unequal  diameter  may  be  obtained  by  meas- 
uring from  the  near  edge  of  one  to  the  near  edge  of  the  other  and 
adding  one-half  the  diameter  of  each.  The  distance  from  an  edge 
or  surface  to  the  center  of  a  hole  may  be  had  by  adding  one-half 
the  diameter  of  the  hole  to  the  distance  from  the  edge  or  surface 
to  the  near  edge  of  the  hole. 

Fig.  311  shows  an  object  the  form  of  which  makes  it  necessary 
to  use  the  caliper  in  measuring  the  distance  between  the  centers 


MEASUREMENTS 


273 


of  the  two  holes.  The  corners  of  cast  parts  are  usually  rounded 
or  filleted.  The  radii  of  these  curves  are  not  easily  measured,  but 
usually  it  is  unnecessary  to  measure  them  accurately.  The  radii 
of  small  fillets  may  often  be  estimated  entirely  by  eye  or  the 
scale  held  against  the  object  at  one  point  of  tangency  and  the 
radius  estimated  by  placing  the  thumb  nail  at  the  division  on  the 


FIG.  313.     TYPICAL  OBJECTS  FOR  FIRST  DRAWING  FROM  MODEL 

scale  opposite  the  other  tangent  point.  A  very  satisfactory 
method  applicable  in  some  cases  is  to  place  the  object  over  a  sheet 
of  paper  and  trace  around  the  corner  or  fillet  with  a  sharp  pencil. 
The  center  of  the  arc  thus  obtained  may  be  found  by  trial  with 
the  dividers  and  the  radius  measured. 

Checking.  Where  a  number  of  detail  dimensions  have  been 
taken  which  make  up  the  length  of  a  larger  detail  or  the  whole 
length  of  the  object,  this  over-all  dimension  should  be  checked 
by  direct  measurement  as  well  as  by  addition  of  the  detail 
dimensions. 


DATA  FOB  DRAWING  PLATE  39 

Given :     A  simple  machine  part  or  model  preferably  finished 
all  over.    Fig.  313  shows  typical  objects  for  this  plate. 
Required:     To  make  a  freehand  orthographic  sketch. 


274  MECHANICAL  DRAWING 

Instructions:  The  following  is  a  brief  summary  of  the  steps 
arranged  in  sequential  order  to  be  taken  in  making  a  sketch  from 
the  object.  It  is  believed  that  by  carefully  observing  the  steps 
of  this  outline  the  draftsman  will  be  able  to  make  the  sketch  com- 
plete and  accurate  with  a  minimum  amount  of  effort,  and  to  do 
the  work  in  the  least  amount  of  time. 

1.  Select  views. 

2.  Draw  views  (proportioning  details  by  eye  without  taking 
dimensions). 

8.  Plan  dimensions — draw  dimension  and  extension  lines. 

4.  Draw  arrowheads. 

5.  Take  dimensions  from  the  object  and  place  figures. 

6.  Mark  finished  surfaces. 

7.  Print  all  notes,  including  the  name  of  the  part  drawn,  the 
number  required,  and  the  material  from  which  each  part  is  to  be 
made. 


:     For  convenience  in  forming 
.the  letters  they  are  divided  into 
.strokes,     Three  things  should  be 
remembered  about  the  strokes 
.for  each  letter,  (I)  the  number-  : 


FIG.  314.    LETTERING  PLATE  39 


DATA  FOR  LETTERING  PLATE  39 

Given:     Plate  39  to  reduced  size.    Fig.  314. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


t 

MEASUREMENTS  275 

DATA  FOB  DRAWING  PLATE  40 
Given:     The  orthographic  sketch.    Plate  39. 
Required:     To  make  a  mechanical  drawing  from  Plate  39. 


\of  strokes  (2)  the  order  in  wh/ch 
'.they  ore  made  (3)  the  direction 
.in  which  each  stroke  is  drawn, 
:     Second  only  in  importance  to 
.the  forms  of  the  letters  is  their 


Fi«.  315.    LETTERING  PLATE  40 


^relation  to  each  other,  The  finals: 
litest  of  good  spacing  is  legibility.  ~ 
z  All  strokes  should  be  made  z 
ZI/K///?  the  hand  and  arm  in  th&  ~ 
"Lsame  position.  123456789''. 


FIG. •?"*?.    LETTERING  PLATE  41 
DATA  ?OE  LETTERING  PLATE  40 
Given:     Plate  40  to  reduced  size.    Fig.  315. 
Required :     To  make  the  plate  to  an  enlarged  scale. 


276  MECHANICAL  DRAWING 

DATA  FOE  DRAWING  PLATE  41 

Given :     The  mechanical  drawing,  Plate  40. 
Required:    To  make  a  tracing  from  Plate  40. 


Fio.  317.    TYPICAL  MODEL  OF  COMPLETE  MACHINE 

DATA  FOB  LETTERING  PLATE  41 

Given:     Plate  41  to  reduced  size.    Fig.  316. 
Required:    To  make  the  plate  to  an  enlarged  scale. 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  42 

The  model  for  this  plate  should  be  a  complete  machine  or 
some  unit  of  a  machine  which  is  composed  of  several  Darts.    The 


MEASUREMENTS 


277 


parts  of  the  model  then  can  be  divided  into  several  groups  and 
each  group  assigned  to  a  student.*  Fig.  317  shows  a  typical 
model,  the  parts  of  which  are  divided  into  groups.  Fig.  318.  The 
detail  drawihgs  of  this  model  will  be  used  later  (Plate  48)  in 
making  an  assembly  drawing. 


FIG.  318.    SHOWING  GROUPS  OF  PARTS  OF  MACHINE  FOR  ASSIGNMENT 


DATA  FOR  DRAWING  PLATE  42 

Given :    A  part  or  group  of  parts  of  a  machine. 

Required:  To  make  an  orthographic  sketch  of  each  part 
assigned  by  the  instructor. 

Instructions:  In  making  the  sketches  proceed  according  to 
the  steps  outlined  for  Plate  39. 

More  than  one  part  may  be  drawn  on  each  sheet,  provided  the 
views  are  not  too  small  or  crowded  too  closely  together. 

In  drawing  and  dimensioning  these  objects  the  student  should 
check  each  detail  with  the  parts  which  are  related  to  it  or  depend 
upon  it  in  any  way. 

Note  should  be  made  of  the  name  of  each  part,  the  number 
required,  and  the  material  from  which  it  is  made. 

*  This  plan  gives  best  results  when  there  are  from  3  to  6  students 
working  on  each  model. 


278  MECHANICAL  DRAWING 

DATA  FOR  LETTERING  PLATE  42 

Given:     Plate  42  to  reduced  size.    Fig.  319. 
Required :     To  make  the  plate  to  an  enlarged  scale. 


z  Shifting  of  the  arm  to  obtain  z 
^advantageous  positions  for  draw= 
^Ling  strokes  in  different  direct-  z 
~/of?s  AS  a  habit  which  will  never  z 
i  lead  to  rapid  production  of z 


FIG.  319.    LETTERING  PLATE  42 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  43 

When  making  the  mechanical  drawing,  all  of  the  parts  in  each 
group  should  be  drawn  on  one  sheet  if  possible.  The  arrangement 
of  the  views  should  be  such  as  to  make  the  best  use  of  the  space 
available,  and  at  the  same  time  produce  a  pleasing  effect  for  the 
sheet  as  a  whole.  This  will  require  careful  study.  The  solution 
will  depend  largely  on  the  draftsman 's  judgment.  In  general,  it 
may  be  said  that  the  distance  between  views  of  different  objects 
should  be  greater  than  that  between  views  of  the  same  object. 
The  enclosing  rectangles  for  each  view  may  be  drawn  lightly  to 
make  sure  that  sufficient  space  has  been  allowed  for  the  drawing 
of  all  parts  before  drawing  the  views,  or  better  yet,  a  rectangle 
equal  in  size  to  the  enclosing  rectangle  for  the  ^  Jews  of  each  part 
may  be  cut  from  paper  and  moved  about  until  the  best  possible 
arrangement  is  secured. 

Before  starting  to  plan  the  arrangement  of  the  sheet,  the  areas 
occupied  by  the  bill  of  material  and  the  title  block  should  be  laid 
out.  The  bill  of  material  as  shown  in  Fig.  279  contains  the 


MEASUREMENTS  279 

reference  figure  corresponding  to  the  one  placed  near  the  views 
of  the  object,  the  name  of  the  object,  the  number  required,  and 
the  materials  from  which  it  is  made.  The  width  of  the  bill  of 
material  is  equal  to  the  width  of  the  title  block,  and  the  height 
depends  upon  the  number  of  parts  to  be  listed.  See  Fig.  279  for 
detail  dimensions. 

In  some  shops  the  information  referred  to  above  is  given  for 
each  part  near  the  views  of  that  part  and  is  called  a  sub-title. 

The  title  for  a  sheet  containing  the  drawings  of  several  parts 
must  be  a  general  one  in  which  the  word  ' '  details ' '  usually  takes 
the  place  of  the  name  of  the  part  drawn.  See  Fig.  322.  It  is 
often  convenient  to  use  different  scales  for  the  various  objects, 
in  which  case  the  scale  for  each  should  be  printed  with  the  views 
of  that  part  and  the  words,  "  Scales  as  noted, "  printed  in  the 
usual  place  in  the  title. 


'.—  letters  and  at  the  same  time    ~ 
\it  wi.ll  prevent  the  develooment    ~ 
\of  the  snap  and  swing  which 
\gives  the  character  to  what  is    z 
\recognized  as  good  lettering. 


FIG.  320.    LETTERING  PLATE  43 

DATA  FOE  DRAWING  PLATE  43 
Given:  The  orthographic  sketch,  Plate  42. 
Required:  To  make  a  mechanical  drawing  from  Plate  42. 

DATA  FOE  LETTERING  PLATE  43 
Given:  Plate  43  to  reduced  size.  Fig.  320. 
Required :  To  make  the  plate  to  an  enlarged  scale. 


280  MECHANICAL  DRAWING 

DATA  TOR  DRAWING  PLATE  44 

Given:     The  pencil  mechanical  drawing.  Plate  43. 

Required:     To  make  a  tracing  of  Plate  43. 

Instructions:  The  width  of  the  top  and  left  sides  of  the  rec- 
tangle enclosing  the  bill  of  material  and  the  vertical  division  lines 
should  be  object  line  width  (  ^  ").The  horizontal  lines  between 
lines  of  lettering  should  be  center  line  width 


DATA  FOR  LETTERING  PLATE  44 

Given:    Plate  44  to  reduced  size.    Fig.  321. 
Required:     To  make  the  plate  to  an  enlarged  scale. 


~    A  drawing,  Ihe  mechanical 
^Lpart  of  which  is  well  executed, 
^.may  have  its  appearance  spoiled^, 
^by  poor  lettering.       Lines  should^ 
black  and  of  uniform  weight,  ~ 


FIG.  321.    LETTERING  PLATE  44 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  45 

One  of  the  problems  of  the  draftsman  is  to  make  detail  draw- 
ings from  the  original  layout  of  a  machine  in  which  the  parts  are 
shown  assembled.  On  this  assembly  drawing  some  important 
dimensions  may  be  given,  others  may  be  scaled  from  the  drawing, 
and  the  remainder  must  be  supplied  by  the  draftsman  himself. 
Since  this  course  does  not  presuppose  a  knowledge  of  design,  all 
necessary  dimensions  will  be  given  on  the  assembly  drawing  from 
which  the  student  draws  this  plate. 


MEASUREMENTS 


281 


o 

si 

CD      < 

£L.UJ 


284 


MECHANICAL  DRAWING 


The  reading  of  the  assembly  drawing  to  get  the  correct  form 
for  each  detail  will  in  most  cases  require  careful  study.  The  dif- 
ferent parts  may  be  distinguished  when  in  section  by  various 
erosshatching  for  different  metals  and  by  the  sectioning  of  adja- 
cent parts  at  opposite  angles.  But  even  with  this  aid  the  differ- 
ent views  must  be  compared  carefully  to  check  the  first  impres- 
sion gained  of  the  form  of  each  part  and  to  make  sure  that  no 
detail  has  been  overlooked.  Each  part  of  the  object  must  be 
dimensioned  completely.  It  is  not  sufficient  to  give  a  dimension 
on  the  views  of  one  part  and  omit  the  same  dimension  on  the  views 
of  another  part,  even  though  it  is  evident  that  the  dimension  is 
the  same  on  both. 


FIG.  325.    LEVELING  SCREW 


DATA  FOR  DBA  WING  PLATE  45 

Given:  An  assembly  drawing  of  a  Leveling  Screw,  Fig. 
325 ;  a  flap  valve,  Fig.  326 ;  and  a  letter  press,  Fig.  327. 

Required:  To  make  freehand  orthographic  detail  sketch 
of  the  object  shown  in  Fig.  325,  326,  327,  or  any  similar  object 
as  assigned  by  the  instructor. 


MEASUREMENTS 


385 


e 

I 


286 


MECHANICAL  DRAWING 


FIG.  327.    LETTER  PRESS 


ASSEMBLY 
BENCH  DRILL  PRESS 


FIG.  328.     TYPE  PROBLEM.     BENCH  DRILL  PRESS 


(287) 


288  MECHANICAL  DRAWING 

A  Flap  Valve  is  used  to  allow  a  liquid  or  gas,  such  as  water 
or  steam,  to  flow  in  one  direction  through  a  pipe  but  not  in  the 
other.  Its  parts,  as  designated  by  figures  in  circles  in  Fig.  326, 
are  named  as  follows : 

1.  Body.     2.  Cap.      3.  Valve.     4.  Arm.      5.  Cap  Screw. 

A  Leveling  Screw  is  used  for  leveling  up  work  on  a  planer. 
Its  parts,  as  designated  by  figures  in  circles  in  Fig.  325,  are 
named  as  follows : 

1.  Base.  2.  Screw.  3.  Cap. 

Fig.  327  shows  a  Letter  Press.    Its  parts,  as  designated  by 

figures  in  circles,  are  named  as  follows: 

1.  Base.  6.  Bolt. 

2.  Plate.  7.  Nut. 

3.  Yoke  Support.  8.  Clamp. 

4.  Press  Screw.  9.  Button  Head  Screw. 

5.  Hand  Wheel.  10.  Yoke. 


:  Careful  attention  to  detail 
.bined  with  intelligent  and  per-  ~ 
.sistent  practice  will  do  much  to  z 
.offset  lack  of  talent  for  lettering^ 
.2357  9861  45309  728695  = 


FIG.  329.    LETTERING  PLATE  45. 


DATA  FOR  LETTERING  PLATE   45 


Given:     Plate  45  to  reduced  size.    Fig.  329 
Required:     To  make  the  plate  to  an  enlarged  scale. 


MEASUREMENTS 


289 


DATA  FOR  DRAWING  PLATE  46 

Given:     The  orthographic  sketch.    Plate  45. 
Required:     To   make   a   pencil  mechanical   drawing  from 
Plate  45. 

DATA  FOR  DRAWING  PLATE  47 

Given:     The  pencil  mechanical  drawing.    Plate  46. 
Required:     To  make  a  tracing  of  Plate  46. 


FIG.  330A.    DETAILS  OF  BEXCH  GRINDER 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  48 
An  Assembly  or  General  Drawing  is  made  for  showing  the 
position  and  relation  of  parts  of  a  machine  or  structure.    Usually 
only    the    most   important    dimensions    are    given.      Example: 
Fig.  328. 


290 


MECHANICAL  DRAWING 


DATA  FOR  DRAWING  PLATE  48 

Given :     The  detail  drawings  of  a  bench  grinder,  Figs.  330A 
and  330B;  screw  punch,  Fig.  331. 

Nut 


I  Wanted     Head/ess      ff./f.  Cap  Screws 


Teefffesf 


" 


FIG.  330B.     DETAILS  OF  BENCH  GRINDER 


MEASUREMENTS 


291 


Section  showing  I?  a//  helef 
in  place  by  beaded  edge 
of  socket 


Ho30  Dr/7/ 
Vse  special  ftx>/    Use  spec/a/ dri// 


locate  groore  offer  assembling 

F 


FIG.  331.    DETAILS  OF  SCREW  PUNCH 


292  MECHANICAL  DRAWING 

Required:  To  make  a  pencil  mechanical  drawing  from  the 
details  of  the  objects  shown  in  Figs.  330A  and  330B  or  331,  or  any 
similar  problem  assigned  by  the  instructor.  It  is  suggested  that 
an  assembly  drawing  may  be  made  from  the  student  detail  draw- 
ings of  Plate  43. 

DATA  FOB  DRAWING  PLATE  49 

Given:     The  pencil  mechanical  drawing.     Plate  48. 
Required:     To  make  a  tracing  of  Plate  48. 

ARCHITECTURAL  DRAWING 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  50 

The  average  man  who  contemplates  building  a  house  for  him- 
self finds  it  a  great  convenience  to  be  able  to  make  scale  drawings 
of  sufficient  accuracy  to  test  his  ideas  of  the  arrangement  of 
rooms,  dimensions,  proportions,  general  appearance,  etc.,  and  as 
a  means  of  conveying  his  ideas  to  an  architect  or  contractor. 
The  drawings  should  consist  of  floor  plans  and  views  of  each  side 
of  the  house,  known  as  elevations. 

The  general  arrangement  of  rooms  on  the  first  floor  will 
depend  on  such  things  as  the  nature  of  the  site,  the  owner 's  ideas 
of  household  conveniences,  etc.  As  a  general  principle,  the  rooms 
which  are  used  the  largest  percentage  of  time  are  given  the  most 
favorable  location  for  light  and  ventilation.  As  an  example,  the 
living  room  is  quite  frequently  arranged  to  have  a  south  and  east 
exposure. 

In  all  rooms,  the  location  of  furniture,  doors,  windows,  etc., 
should  be  carefully  considered  as  the  plan  for  the  house  is  pro- 
gressing. The  kitchen  in  the  average  small  house  is  planned  to 
save  steps  for  the  housewife.  The  sink,  stove,  table,  and  cup- 
boards should  be  arranged  with  a  view  to  convenience. 

In  the  average  house,  economy  of  space  is  a  feature  worth 
striving  for,  as  the  cost  of  the  house  will  range  from  15  cents  to 
22  cents  per  cubic  foot. 

The  plan  of  the  second  floor  will  depend  somewhat  on  that  of 
the  first  floor.  The  partitions  on  the  second  floor  should  be 


MEASUREMENTS 


293 


FIG.  331A.    EXTRA  PLATE 


FIG.  331B.    EXTRA  PLATE 


294 


MECHANICAL  DRAWING 


Half  L  op  Joinf 
in  Wrought  Iron 


Frenf  ILeg  nof  5horrr?    ^ 
"•T 


FIG.  331C.     EXTRA  PLATE 


MEASUREMENTS 


295 


directly  over  those  on  the  first  floor,  as  far  as  this  arrangement 
can  be  made.  The  position  of  the  stairs  must  be  considered  and 
space  enough  allowed  for  steps  to  reach  the  second  floor.  As  a 


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FIG.  332.     FIRST  FLOOR  PLAN  OF  HOUSE 


guide  in  laying  out  stairs,  the  sum  of  the  tread  and  rise  should 
bo  about  17"  to  17£"T  with  a  tread  not  less  than  9"  wide  for  front 
stairs  or  8"  wide  for  back  stairs. 


296 


MECHANICAL  DRAWING 


In  locating  the  bathroom,  care  must  be  taken  to  make  it 
possible  for  the  pipes  and  drains  to  lead  down  through  the  walls 
of  the  first  floor.  In  a  cold  climate  there  is  danger  of  freezing 


FIG.  333.    SECOND  FLOOR  PLAN  OF  HOUSE 

if  they  are  put  through  an  outside  wall.  Wherever  possible, 
plumbing  should  be  minimized.  It  is  well,  therefore,  to  have 
bathroom,  kitchen,  and  basemeht  water  and  sewer  connections  in 
the  same  vertical  wall. 


MEASUREMENTS 


297 


298 


MECHANICAL  DRAWING 


t 
o 

£> 

$'* 
t;\ 

£«5 

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m 


MEASUREMENTS 


299 


A  bathroom  should  not  be  less  than  5'  6"  one  way  with  not 
less  than  49  sq.  ft.  of  floor  space.  In  planning  bedrooms,  there 
should  be  windows  on  two  adjacent  sides,  if  possible,  to  provide 
light  and  good  ventilation.  Bedrooms  may  be  as  small  as  9'  6" 


<fe 


FIG.  336.     DETAILS  OF  DOOR  AND  WINDOW 


by  11'  6",  if  well  planned.  The  spaces  for  beds,  dressers,  etc., 
should  be  considered  with  reference  both  to  natural  and  artificial 
light  and  to  necessary  wall  space.  All  upstairs  rooms  should  be 
provided  with  ample  closet  room.  Other  considerations  entering 
into  the  problem  of  planning  the  upstairs  is  the  type  of  roof, 
position  of  ehimneys,  etc.  Electric  wiring,  especially  for  outlets, 


300  MECHANICAL  DRAWING 

and  pipes  for  either  hot  air  or  for  steam  or  hot  water  should  be 
thought  out  as  the  plans  for  the  two  floors  are  made. 

When  the  floor  plans  have  been  arranged,  the  elevation  and 
possibly  a  perspective  of  the  house  should  be  drawn.  If  the 
appearance  is  not  satisfactory,  the  plans  for  the  floors  may  need 
altering.  It  is  not  uncommon  for  plans  to  be  worked  over  a 
number  of  times  to  meet  the  needs  of  both  owner  and  builder. 


DATA  FOE  DRAWING  PLATE  50 

Given:  The  two  floor  plans,  the  side  and  front  elevations 
of  a  house,  with  details,  as  shown  in  Figs.  332,  333,  334,  335, 
and  336. 

Required:  To  rearrange  the  floor  plans,  if  desired,  and  to 
design  the  other  side  elevation  and  the  rear  elevation,  or  any 
similar  problems  assigned  by  the  instructor. 

Note.  The  student  may  change  the  elevations  shown  in  Figs. 
334  and  335  if  his  second  floor  plan  demands  a  different  arrange- 
ment of  windows  or  changes  in  the  roof. 

Instructions:  It  will  be  found  very  convenient  to  draw  the 
first  floor  plan  and  then  lay  out  the  plan  of  the  second  floor  on 
transparent  paper  stretched  over  the  first  floor  drawing. 

Many  measurements  are  thus  copied  by  tracing ;  an  accurate 
register  of  all  first  floor  data  in  comparison  with  that  for  the 
second  floor  is  thus  made,  and  mistakes  are  less  apt  to  occur.  In 
a  similar  manner  the  elevations  may  be  drawn  over  the  plans  but 
of  course  in  this  case  all  the  vertical  measurements  must  be  made 
with  a  scale.  The  particular  advantage  in  this  method  of  draw- 
ing elevation  views  is  to  secure  correct  horizontal  dimensions, 
window  and  door  positions,  etc. 

PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  51 

After  the  construction  of  a  house  has  progressed  until  the 
walls  are  covered  with  plaster  on  the  inside  and  with  siding  on 
the  outside,  and  after  the  roof  is  in  place,  the  framing  construc- 
tion is  not  apparent.  But  in  order  to  build  a  house  which  will 
stand  firm  in  wind  and  will  not  let  in  the  rain,  the  carpenter 


ARCHITECTURAL  DRAWING 


301 


M 

is 


302 


MECHANICAL  DRAWING 


must  consider  carefully  problems  of  framing  construction.  Figs. 
338,  339,  340,  and  341  give  in  detail  typical  construction  for  a 
small  house. 


FIG.  338.    PERSPECTIVE  OP  PARK  HOUSE 


FIG.  339.    PERSPECTIVE  OF  FRAMING  CONSTRUCTION  OF  PARK  HOUSE 


MEASUREMENTS 


303 


DATA  FOE  DRAWING  PLATE  51 

Given:  The  perspective  sketches,  Figs.  338  and  339;  the 
plan,  Fig.  340 ;  and  the  cornice  detail,  Fig.  341,  for  a  small  park 
house. 

Required:  To  draw  the  orthographic  views  showing  the 
framing  and  details  of  construction  for  the  park  house  or  any 
similar  object  as  assigned  by  the  instructor. 


FIG.  340.    PLAN  OF  PARK  HOUSE 


304 


MECHANICAL  DRAWING 


A.  Plate  2x4  . 

6.  6/rt  2-ex4.Mrf/sdirrfo posts 

C.  Frieze 

0  Furring  strips  g  x  A 

£.  flfov/d/rra  $'  * 

/"  //a/ ting  blocks 

6  ft/ting,  between  ratters 

D '  Furring  strips  £"*//' 


/£  sa.  strips  screwed  to  cap. 
postst  cind  soffit  for 
fastenings 


Oefait  of5heath/nq 


Det#/l  of  Sill  and  foot/rigs 


FIG.  341.    CORNICE  DETAILS 


CHAPTER  VI 


ISOMETRIC  AND  CABINET  DRAWING 
PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  52 

Isometric  Drawing  is  a  mechanical  method  of  representing 
objects  pictorially.  The  object  may  appear  somewhat  distorted 
when  drawn  by  this  method,  but  to  one  who  is  not  accustomed 
to  reading  orthographic  drawings  or  for  one  who  is  unable  to 
make  a  good  freehand  perspective  drawing,  it  serves  the  purpose 
of  making  clear  the  general  form  of  the  object.  By  placing 


FIG.  342.    THE  CUBE  IN  ISOMETRIC 

dimensions  on  it  the  isometric  drawing  may  be  used  as  a  working 
drawing. 

Fig.  342  shows  the  isometric  of  a  cube.  The  cube  appears  as 
shown  in  this  figure  when  it  is  viewed  (as  in  orthographic  draw- 
ing) with  a  diagonal  of  the  cube  coincident  to,  or  parallel  with, 
the  line  of  sight.  When  in  this  position  the  three  edges  meeting 
in  the  near  corner  are  represented  by  lines  120°  apart. 

The  three  lines  120°  apart  are  the  axes  parallel  to  which  all 
measurements  are  made  in  isometric  drawing. 

-Non-Isometric  Lines.  A  line  which  is  not  parallel  to  one  of 
the  three  axes  is  a  non-isometric  line.  A  non-isometric  line  is 
drawn  by  referring  points  on  the  line  to  the  axes  by  means  of 

305 


306 


MECHANICAL  DRAWING 


coordinates.  Fig.  343  shows  a  rectangular  solid  on  the  top  face 
of  which  is  a  non-isometric  line  having  a  curved  and  a  straight 
portion.  The  position  of  the  point  D  is  determined  in  the 
isometric  by  transferring  lengths  AB  and  AC  from  the  ortho- 
graphic views  with  the  dividers  and  drawing  lines  B  D  and  C  D 
parallel  to  the  axes.  In  some  cases  where  a  figure  containing  non- 
isometric  lines  is  to  be  drawn,  it  is  convenient  to  enclose  the  figure 
in  a  rectangle.  The  hexagon  in  the  side  face  of  the  rectangular 
solid,  Fig.  343,  and  the  circle  enclosed  in  a  square,  Fig.  343,  are 
illustrations  of  such  cases. 


FIG.  343.    LOCATING  POINTS  ON  NON-ISOMETRIC  LINES  USING  Two 
COORDINATES 


When  non-isometric  lines  do  not  lie  in  a  face  of  a  rectangular 
solid,  three  coordinates  are  necessary  to  locate  points  on  each 
line.  In  drawing  the  isometric  of  the  frustum  of  the  hexagonal 
pyramid,  Fig.  344,  the  base  is  first  enclosed  in  a  rectangle  and  the 
points  on  the  top  face  are  located  by  three  coordinates  as  shown. 
The  lengths  A  B,  B  D,  and  D  E  are  taken  from  the  orthographic 
views  and  laid  off  on  the  isometric  in  the  directions  parallel  to 
each  of  the  three  axes,  respectively. 

Isometric  Circles.  Circles  may  be  drawn  by  locating  points 
as  described  above,  or  by  the  four-center  method  shown  in  Fig. 
345.  Point  A,  the  center  of  the  smaller  arc,  is  located  by  laying 
off  AB  =  BC.  The  center  D  for  the  larger  arc  is  located  by 
drawing  A  D  through  A  perpendicular  to  B  E.  The  other  centers 


FIG.  344.    LOCATING  POINTS  ON  NON-ISOMETRIC  LINES  USING  THREE 

COORDINATES 


FIG.  345.     A  FOUR-CENTER  METHOD  TOR  DRAWING  CIRCLES  IN  ISOMETRIC 

(307) 


FIG.  346.    METHODS  OF  DRAWING  CIRCLES  AND  ARCS 


r> 

-rn 

! 

it 

i 

i| 

i 

1  1 

l  

31 

J™j! 

-t—j 

_  staif  of  5ecfton  on  C-O 

Corner  Construction 


FIG.  347.    TYPE  PROBLEM.     STUDY  TABLE.     ORTHOGRAPHIC  VIEWS 

(308), 


FIG.  348.    TYPE  PROBLEM.    ISOMETRIC  DRAWING  OF  STUDY  TABLE 


FIG.  349.    TYPE  PROBLEM.    CABINET  DRAWING  OF  STUDY  TABLF- 

Y309) 


310 


MECHANICAL  DRAWING 


are  located  in  a  similar  manner.  The  arcs  are  tangent  at  the 
point  F.  The  four-center  method  is  an  approximation  and  is 
usually  suitable  only  for  full  circles.  When  an  arc  is  drawn 
which  must  pass  through  certain  points  the  plotting  method  is 
preferable.  Fig.  346. 


Defai/of 
Corner  Construction 


f  I 


FIG.  350.     TABORET 


DATA  FOR  DRAWING  PLATE  52 

Given:     The  orthographic  views  of  a  taboret.    Fig.  350. 

Required:  To  make  an  isometric  (or  cabinet  drawing)  of 
the  object  shown  in  Fig.  350  or  any  similar  object  assigned  by 
the  instructor.  For  cabinet  drawing  instructions  see  page  314. 

Instructions: 

1.  Make  an  orthographic  drawing  to  scale. 

2.  Draw  lines  for  the  isometric  drawing  in  the  directions  of 
the  three  axes :   One  vertical,  and  one  each  to  the  right  and  to  the 
left,  making  30°  with  the  horizontal. 


ISOMETRIC  AND  CABINET  DRAWING 


311 


3.  Decide  which  of  the  general  dimensions  of  the  object  is 
to  be  measured  in  the  direction  of  each  axis. 

4.  Locate  a  certain  point,  usually  an  extreme  corner  of  the 
object,  at  the  intersection  of  the  lines  drawn  as  directed  in  2. 


FIG.  351.    TYPE  PROBLEM.    PLANING  JIG  FOR  &OD  BRASS. 

VIEWS 


ORTHOGRAPHIC 


5.  Transfer  actual  lengths  from  the  orthographic  drawing 
with  the  dividers,  taking  care  to  lay  them  off  in  the  direction  of 
the  proper  axis. 

6.  Draw  the  necessary  lines  through  the  points  located,  re- 
membering that  lines  of  the  object  which  are  parallel  to  a  general 
dimension  of  the  object  should  be  drawn  parallel  to  the  axis 
representing  that  dimension. 

7.  All  other  lines  must  be  determined  by  locating  points  as 
described  on  page  306. 


FIG.  352.     TYPE  PROBLEM.     ISOMETRIC  OF  JIG  FOR  ROD  BRASS 


(312)    pIQ  353^    TYPE  PROBLEM.    CABINET  OF  JIG  FOR  ROD  BRASS 


ISOMETRIC  AND  CABINET  DRAWING 


313 


DATA  FOR  DRAWING  PLATE  53 

Given:     The  orthographic  views  of  a  crosshead  brass. 


Fig. 


354. 


Required:  To  make  an  isometric  (or  cabinet  drawing)  of 
the  object  shown  in  Fig.  354,  or  any  similar  problem  assigned 
by  the  instructor.  For  cabinet  drawing  instructions  see  page  314. 


FIG.  354.    CROSSHEAD  BRASS 
Instructions: 

1.  Proceed  in  drawing  the  straight  lines  as  for  the  preceding 
plate. 

2.  To  draw  the  circles  by  the  four  center  method,  first  deter- 
mine the  center  by  the  method  of  coordinates. 

3.  Draw  a  figure  representing  a  square  which  just  circum- 
scribes the  circle.     Care  must  be  taken  to  draw  this  figure  so 
that  it  will  appear  to  lie  in  the  same  face  of  the  object  as  the 
circle  to  be  drawn.    The  direction  of  the  sides  of  this  figure  will 
correspond  to  those  representing  one  of  the  faces  of  the  cube. 
Fig.  345. 

4.  Draw  the  curves  by  the  method  given  under,  "Isometric 
Circles/' 


314  MECHANICAL  DRAWING 

CABINET  DRAWING 
PREPARATORY  INSTRUCTIONS  FOR  DRAWING  PLATE  54 

Cabinet  Drawing  is  similar  to  isometric  in  that  measurements 
are  made  parallel  to  three  axes.  One  of  the  axes  is  horizontal, 
the  second  vertical,  and  the  third  45°  to  the  horizontal.  Fig.  355. 
Actual  lengths  are  measured  parallel  to  the  horizontal  and  ver- 
tical axes  and  one-half  the  actual  lengths  are  measured  parallel 


FIG.  355.     CABINET  DRAWING  OF  CUBE 


FIG.  356. 


EXAMPLE  OF  AN  OBJECT  WITH  CIRCLES  AND  ARCS  PARALLEL  TO 
ONE  PLANE 


to  the  45°  axis.  It  should  be  evident  that  objects  which  involve 
the  drawing  of  irregular  shaped  figures  which  are  located  in  or 
parallel  to  the  front  surface  of  the  object  can  be  represented 
more  easily  by  cabinet  than  by  isometric,  inasmuch  as  such 
figures  will  be  drawn  in  their  true  form  in  a  cabinet  drawing. 
For  example,  an  object  which  has  a  number  of  circles  parallel 
to  one  plane  is  more  easily  represented  in  cabinet  than  in 
isometric,  since  the  circles  can  be  drawn  with  the  compass. 
Fig.  356. 


ISOMETRIC  AND  CABINET  DRAWING 
DATA  FOR  DRAWING  PLATE  54 


315 


Given:     The  orthographic  views  oi  a  taboret.    Fig.  350. 
Required :     To  make  a  cabinet  drawing  of  the  object  shown 
in  Fig.  350,  or  any  similar  object  assigned  by  the  instructor. 


FIG.  357.    Am  STARTER  BEARING 


Instructions: 


1.  Make  an  orthographic  drawing  to  scale. 

2.  Draw  lines  for  the  cabinet  drawing  in  the  direction  of  the 
three  axes;  one  vertical,  one  horizontal,  and  one  at  45°. 

3.  Decide  upon  the  general  dimension  of  the  object  .to  be 
measured  in  the  direction  of  each  axis. 

4.  Locate  a  certain  point,  usually  an  extreme  corner  of  the 
object,  at  the  intersection  of  the  lines  drawn  as  directed  in  2. 

5.  Transfer  actual  lengths  from  the  orthographic  drawing 
with  the  dividers  for  the  measurements  parallel  to  the  horizontal 
and  vertical  axes,  and  one-half  actual  lengths  for  the  measure- 
ments parallel  to  the  45°  axis. 


316 


MECHANICAL  DRAWING 


6.  Draw  the  necessary  lines  through  the  points  located,  re- 
membering that  the  lines  of  the  object,  which  are  parallel  to  a 
general  dimension  of  the  object,  should  be  drawn  parallel  to  the 
axis  representing  that  dimension. 

7.  Lines  not  parallel  to  the  axes  must  be  located  by  the  same 
method  of  plotting  points  used  for  the  isometric  drawing  and 
described  on  page  306. 


FIG.  •  358.     TYPE  PROBLEM.     SPAKKER  BODY 


DATA  TOR  DRAWING  PLATE  55 

Given:  The  orthographic  views  of  a  crosshead  brass.  Fig. 
354. 

Required:  To  make  a  cabinet  drawing  of  the  object  as 
shown  in  Fig.  354,  or  any  similar  problem  assigned  by  the 
instructor. 

Instructions: 

1.  Proceed  in  drawing  the  straight  lines  as  for  the  preceding 
plate. 


ISOMETRIC  AND  CABINET  DRAWING 


317 


2.  The  circles  which  are  in  or  parallel  to  the  front  face  of 
the  object  may  be  drawn  with  the  compass.  All  others  must  be 
determined  by  plotting  points.  The  object  should  be  placed,  if 
possible,  so  that  the  circles  can  be  drawn  with  the  compass. 

DATA  FOR  DRAWING  PLATE  56 

Given:  The  orthographic  views  of  a  sparker  body.  Fig. 
358. 

Required:  To  make  a  cabinet  drawing  of  the  object  shown 
in  Fig.  358,  or  any  similar  object  assigned  by  the  instructor. 


FIG.  359.    BOSCH  MAGNETO  CAM 


Instructions: 

1.  Make  an  orthographic  drawing  to  scale.  Draw  lines  for 
the  cabinet  drawing  in  the  direction  of  the  three  axes;  one  ver- 
tical, one  horizontal,  and  one  to  the  right  or  the  left,  making  45° 
with  the  horizontal. 


318  MECHANICAL  DRAWING 

2.  Transfer  measurements  by  the  same  general  method  used 
in  isometric,  laying  off  only  one-half  the  actual  lengths  in  the 
direction  of  the  45°  axis. 

3.  Circles  or  curves  in  the  front  face  of  the  object  or  planes 
parallel  to  the  front  face  should  be  drawn  in  their  exact  size  and 
form.    All  other  circles  and  curves  must  be  plotted. 


CHAPTER  VII 

GEOMETRICAL  CONSTRUCTIONS 
PROBLEM  1 

Given:     A  straight  line  or  arc  AB. 
Required:     To  bisect  A B.    Fig.  360. 


FIG.  360.    To  BISECT  A  LINE  OR  ARC 

Instructions:  With  A  and  B  as  centers  describe  arcs  inter- 
secting at  C  and  D.  The  line  C  D  bisects  the  straight  line  A  B 
at  F  and  the  arc  at  E. 


a         b         c         d 

FIG.  361.    To  DIVIDE  A  LINE  INTO  A  NUMBER  OF  EQUAL  PARTS 

PROBLEM  2 

Given:     A  straight  line  AB. 

Required:     To  divide  AB  into  any  number  of  equal  parts, 
as  five.    Fig.  361. 

319 


320 


MECHANICAL  DRAWING 


Instructions:  Draw  line  A  C  at  any  angle  with  AB  and  lay 
off  on  it  five  equal  spaces,  using  any  convenient  unit.  Draw 
5  B  and  parallels  to  it  through  1,  2,  3, 4.  a,  b,  c,  d  are  the  required 
divisions. 

Note.  A  line  such  as  AB  in  Problems  1  and  2  may  be 
divided  by  means  of  the  dividers,  as  described  on  page  129. 

PROBLEM  3 

Given :    An  angle  ABC. 

Required:     To  bisect  angle  ABC.    Fig.  362. 


FIG.  362.    To  BISECT  AN  ANGLE 

Instructions:    With  B  as  a  center,  draw  an  arc  AC  of  any 
radius.    With  A  arid  C  as  centers  describe  arcs  of  equal  radius 
intersecting  in  D.    B  D  bisects  the  angle  ABC. 
c 


FIG.  363.    To  TRISECT  A  EIGHT  ANGLE 


PROBLEM  4 


Given :    A  right  angle  ABC. 

Required:     To  trisect  angle  ABC.    Fig.  363. 


GEOMETRICAL  CONSTRUCTIONS 


321 


Instructions:  First  Method.  With  B  as  a  center,  draw  an 
arc  A  C  of  any  radius.  With  A  and  C  as  centers  and  the  same 
radius,  draw  arcs  B  D  and  B  E.  The  angles  thus  formed  are  30°. 


FIG.  364.    To  TRISECT  A  EIGHT  ANGLE  WITH  THE  TRIANGLE 

Second  Method.  An  angle  may  be  divided  into  any  number 
of  equal  parts  by  drawing  an  arc  such  as  AC  in  Problems  3 
and  4  and  stepping  off  equal  distances  on  the  arc,  with  the 
dividers. 


FIG.  365.     To  CONSTRUCT  A  SQUARE 

PROBLEM  5 

Given:     The  length  of  the  side  of  a  square,  AB. 
Required:     To  construct  the  square.    Fig.  365. 


322 


MECHANICAL  DRAWING 


Instructions:  First  Method.  Draw  arc  B  D  C  with  A  B  as  a 
radius.  Bisect  arc  BDC  (Problem  1).  AD  is  now  at  right 
angles  to  AB.  With  centers  at  D  and  B  draw  arcs  of  radius 
AB  intersecting  in  the  fourth  corner  of  the  square. 


FIG.  366.    To  CONSTRUCT  A  SQUARE  WITH  THE  TRIANGLE 


Second  Method.  The  square  may  be  constructed  with  the 
triangles  and  T-square.  Fig.  366.  B  E  and  A  D  are  drawn  at 
right  angles  to  A  B  and  A  E  at  45°  to  AB.  DE  is  drawn 
through  E  parallel  to  AB. 


FIG.  367.    To  CONSTRUCT  AN  OCTAGON 

PROBLEM  6 

Given:     The  length  of  the  side  of  a  regular  octagon. 
Required:     To  construct  the  octagon.    Fig.  367. 


GEOMETRICAL  CONSTRUCTIONS 


323 


Instructions:  First  Method.  Draw  arc  BC  and  AD  and 
bisect  each  as  with  the  lines  P  M  and  Q  N.  Bisect  the  exterior 
right  -angles  and  draw  A  C  and  B  D  equal  to  A  B.  Connect 
C  and  D.  Make  FG  and  EH  equal  to  FE  and  draw  LO 
through  GH.  Make  LG,  GM,  HN,  and  HO  equal  to  CF  or 
E  D.  Connect  C,  L,  M,  N,  0,  and  D. 


FIG.  368.    To  CONSTRUCT  AN  OCTAGON  WITH  THE  TRIANGLE 

Second  Method.  The  octagon  may  be  constructed  with  the 
T-square  and  45°  triangle,  Fig.  368.  BD  is  drawn  at  45°  to 
AB  and  equal  in  length  to  AB.  AM  and  BN  are  drawn  per- 
pendicular to  A  B.  C  D  is  drawn  parallel  to  A  B.  F  H  is  at  45° 
to  AB  and  LO  parallel  to  AB.  The  figure  may  now  be  com- 
pleted by  drawing  the  following  lines  in  the  order  given.  A  C, 
CL,  DO,  LM,  ON,  MN. 


FIG.  369.    To  CONSTRUCT  A  HEXAGON 

PROBLEM  7 

Given:     The  length  of  the  side  of  a  regular  hexagon. 
Required:    To  construct  the  hexagon.    Fig.  369. 


324 


MECHANICAL  DRAWING 


Instructions:  First  Method.  With  a  radius  AB  and  centers 
at  A  and  B,  describe  arcs  meeting  at  C.  With  C  as  center  and 
the  same  radius,  draw  a  circle.  With  the  same  radius  set  off  the 
arcs  B  D,  D  E,  E  F,  F  G,  and  G  A.  The  side  of  the  hexagon 
equals  the  radius  of  the  circumscribed  circle. 


PIG.  370.    To  CONSTRUCT  A  HEXAGON  WITH  THE  TRIANGLE 

• 

Second  Method.  Draw  a  circle  with  a  radius  equal  to  the 
side  of  the  hexagon.  Draw  a  horizontal  or  vertical  diameter  A  B, 
Fig.  370,  depending  on  the  position  of  the  hexagon.  Draw  lines 
with  the  60° -30°  triangle  through  A  and  B,  striking  the  circle. 
Complete  the  figure  by  horizontal  or  vertical  lines,  as  the  case 
may  require. 


FIG.  371.    To  CONSTRUCT  A  TANGENT  TO  A  CIRCLE  THROUGH  A  POINT  OUTSIDE 

THE  CIRCLE 

PROBLEM  8 

Given:    A  circle  and  a  point  outside  the  circle. 
Required:     To  draw  a  tangent  to  the  circle  through  the 
point. 


GEOMETRICAL  CONSTRUCTIONS 


325 


Instructions:  First  Method.  With  a  radius  A  B  and  center 
at  A,  describe  arc  B  C.  With  a  radius  equal  to  the  diameter  of 
the  circle  cut  the  arc  at  C.  The  chord  B  C  strikes  the  circle  in  D, 
the  point  of  tangency.  B  D  is  perpendicular  to  the  tangent  A  D. 
Fig.  371. 


FIG.  372.    To  CONSTRUCT  A  TANGENT  TO  A  CIRCLE  THROUGH  A  POINT  WITH 

THE  TRIANGLE 

Second  Method.  The  tangent  may  be  drawn  with  a  straight 
edge,  as  shown  in  Fig.  372.  The  point  of  tangency  may  be 
found  as  shown  in  Fig.  195,  page  184. 

PROBLEM  9 

Given:     Two  arcs. 

Required:     To  draw  a  line  tangent  to  both  arcs. 

Instructions:  First  Method.  Make  EF  equal  to  AG,  Fig. 
373,  and  draw  a  tangent  through  A  to  the  small  circle  C  F,  as 
in  Problem  8.  Extend  B  H  and  draw  A  G  at  right  angles  to  A  C. 
Join  GK. 


FIG.  373.    To  DRAW  A  LINE  TANGENT 
TO  Two  ARCS 


FIG.  374.  To  DRAW  A  LINE  TAN- 
GENT T6  TWO  ARCS  WITH  THE  TRI- 
ANGLE 


Second  Method.  The  tangent  may  be  drawn  with  a  straight- 
edge, as  shown  in  Fig.  374.  The  points  of  tangency  may  be 
found,  as  shown  in  Fig.  195,  page  184. 


326 


MECHANICAL  DRAWING 


PROBLEM  10 

Given:     Two  straight  lines  intersecting  at  any  angle. 

Required:  To  draw  an  arc  of  given  radius  tangent  to  the 
two  lines.  Fig.  375. 

Instructions:  First  Method.  With  radius  equal  to  the  given 
radius,  draw  arcs  from  two  different  points  in  each  line.  Draw 
tangents  to  each,  pair  of  arcs.  The  intersection  of  these  lines,  H, 
is  the  center  of  the  tangent  arc.  Perpendiculars  from  this  point 
to  the  tangent  lines  locate  the  points  of  tangency  K,  L. 


K  A 


FIG.  375.     To  DRAW  AN  ARC  TAN- 
GENT TO  Two  INTERSECTING  LINES 


FIG.  376.  To  DRAW  AN  ARC  TAN- 
GENT TO  Two  INTERSECTING  LINES 
WITH  THE  TRIANGLE 


Second  Method.  Fig.  376.  Draw  a  line  at  right  angles  to 
each  of  the  intersecting  lines  with  the  triangles,  as  described  on 
page  125.  Lay  off  B  D  and  E  C  equal  to  the  radius  of  arc.  Draw 
lines  DF  and  EF  parallel  to  AB  and  AC,  respectively,  as 
described  on  page  125.  F  is  the  center  of  the  arc.  The  points 
of  tangency  K  and  L  may  be  located  as  described  on  page  184. 


• 


GEOMETRICAL  CONSTRUCTIONS 


327 


PROBLEM  11 

Given:    Two  circles  of  different  diameters. 
Required:     To  draw  a  circle  of  given  radius  tangent  to 
both  circles.    Fig.  377. 


FIG.  377.    To  DRAW  A  CIRCLE  OF  GIVEN  RADIUS  TANGENT  TO  Two  CIRCLES 


Instructions:  From  the  center  of  circle  A  with  a  radius 
equal  to  R  plus  the  radius  of  A,  and  from  the  center  of  B  with 
a  radius  equal  to  R  plus  the  radius  of  B,  draw  two  arcs  inter- 
secting at  C,  which  is  the  center  of  the  required  circle.  The 
points  of  tangency  are  found  by  joining  the  centers  of  the  circles. 

PEOBLEM  12 

Given  :     Two  parallel  straight  lines  A  B  and  C  D. 
Required  :     To  draw  arcs  of  circles  tangent  to  A  B  and  C  D 
and  passing  through  E.    Fig.  378. 


A  B 

FIG.  378.    To  DRAW  ARCS  TANGENT  TO  Two  STRAIGHT  LINES  THROUGH  A 

POINT 

Instructions:  Bisect  BE  and  CE  and  erect  perpendiculars 
to  AB  and  C  D  at  B  and  C.  F  and  G  are  the  required  centers. 
The  arcs  are  tangent  at  E.  This  is  called  a  reverse  or  an  0.  Go 
curve. 


328 


MECHANICAL  DRAWING 


PEOBLEM  13 


Given:     The  length  of  the  major  and  minor  axes  of  the 
ellipse,  0  A  and  0  B. 

Required:     To  construct  the  ellipse. 


FIG.  379.    TRAMMEL  METHOD  OF  DRAWING  AN  ELLIPSE 

Instructions:  Trammel  Method.  Fig.  379.  Mark  off  on  a 
card,  C  D  equal  to  0  B  and  C  E  equal  to  0  A.  Keep  the  trammel 
with  the  point  D  always  on  the  major  axis  and  point  E  always 
on  the  minor  axis.  Move  the  trammel  and  mark  points  opposite 
C  to  form  the  curve. 


FIG.  380.     CONSTRUCTION  METHOD  OF  DRAWING  AN  ELLIPSE 


Second  Method.  Fig.  380.  Draw  circles  of  radii  equal  to  the 
major  and  minor  axes.  Draw  any  radii  OC,  CD,  etc.;  draw 
C  G,  D  H,  etc.,  perpendicular  to  0  A,  and  E  G,  etc.,  parallel 
to  O  A.  G,  H,  etc.,  are  points  on  the  curve. 


INDEX 


Accuracy,  133 

Accuracy  of  measurements,  267 

Acme  threads,  253 

Adjacent  parts,  crosshatching,  of,  229 

Adjustable  square,  266 

Angle  of  inclination,  13 

Angles 

dimensioning,  89 
Architect's  scale,   127 
Architectural  drawing,  292 
Arrangement   of   dimensions   in   ortho- 
graphic sketch,  76 
Arrangement  of  views  on  sheet,  140 
Arrowheads,  38 
Assembly   drawing 

purpose  of,  289 

details  from,  280 
Axes,  derivation  of,   Isometric,  305 

Balancing  a  title,  27,  140 
Bill  of  material,  247 
Bill  of  stock,  226 
Blueprinting,  166 
Board,  drawing,  15,  118 
Bolt,  tap,  258 
Bolts  and  nuts,  255 
Border  line,  172 
Border  rectangle,  20,  133 
Bow  dividers,  132 
Bow  pen,  132,  171. 
Bow  pencil,  132 
Breaks,  conventional,  229 

Cabinet  drawing,   314 
Calipers,  267 
Cap  screw,  258    ' 
Center  lines 

circular,  100 

principal,   100 

radial,  100 

secondary,  100 
Circle 

drawing  with  bow  compass,  171 

sketching,  101 
Circles 

concentric,   in  perspective,  47 

dimensions  of,  100 

Isometric,   306 
Circular  edges,  93 
Cloth,   tracing,    161,    165 
Compass,   170 


Concentric  circles  in  perspective,  47 
Constructive   stage 

in  perspective,  18 

of  orthographic  sketch,  74 

of  mechanical  drawing,  135 
Conventional  cross-sectioning,  230 
Coordinate  paper,  263 
Corners,   representation  of,  69 
Crosshatching 

adjacent  parts,  99,  229 

conventional,  230 
Crosshatch  lines,  172 
Cube 

in  perspective,  13 

measure,  definition  of,   34 

measure  in  new  positions,  57 
Cylinder 

measure,   horizontal,   52 

measure,  in  new  positions,  58 

measure,  vertical,  44 
Cylindrical  surfaces 

dimensions  of,  100 

representation  of,  92 

Development  of  a  surface 

prism,   190 

cylinder,  197 

cone,  203 

pyramid,  212 
Diameter 

measuring  inside,  270 

measuring  outside,  270 
Dimension 

figure  137 

form,  37,  77 

line,  136 
Dimensions 

arrangement      of      in      orthographic 
sketch,  76 

selection  and  arrangement,  263 
Dimensioning 

angles,  89 

general  principles  of,  136 

cylindrical  surfaces  and'  circles,   100 

radius,  150 
Distance 

measuring  center  to  center  of  holes, 
271 

measuring  linear,   268 
Dividers,   130 
Dotted   lines,   171 


329 


330 


INDEX 


Drawing 

an  ellipse,  47 

board,   15,   118 

cabinet,  314 

from  the  object,  261 

Isometric,  305 

paper,  15,  119 
Drawing  instruments 

bow  dividers,  132 

bow  pen,  132 

bow  pencil,  132 

compass,  128 

dividers,  130 

ruling  pen,   167 

Edges 

circular,  representation  of,  93 

inclined,  82 

invisible,  69 

straight,  69 

Ellipse,  to  draw  and  test,  47 
Enclosing  rectangle,  133 
Enclosing  solid  in  perspective,  34 
Engineer's  scale,  127 
Eraser,  132 
Erasing  shield,  132 
Extension  lines,  136 

Fastening  paper  to  board,  15 
Figures 

and   notes,   137 

dimension,  137 
Filling  lettering  pen,  103 
Finish,    methods    of    indicating,    261 
Finishing  stage 

for  mechanical  drawing,  135 

for  orthographic  sketch,  76 

in  perspective,   18 
Folding  rule,   265 
Foot  marks,  30 

Foreshortening,  definition  of,  13 
Fraction  and  whole  number,  137 
Furniture  and  cabinet  problems,  231 

General  drawing,  289 
Geometrical  constructions,   319 

Heads,  arrow,  38 
Heights   of  letters,   137 
Horizon,  definition,  10 
Horizontal  lines,  ruling,  126 

Inch  marks,  30 
Inclination,  angle  of;  13 
Inclined  edges,  82 
Inclined  surfaces,  81 
Ink,  black,   167 


Inking 

order  of,  172 

Inside  diameter,  measuring  of,  270 
Instruments 

drawing,  128 

measuring,   265 
Invisible  edges,  69 
Isometric  drawings,  305 

derivation  of  axes,  305 

Isometric  circles,   306 

Isometric  lines,  305 

locating    points    with    three    coordi- 
nates, 307 

locating  points  with  two  coordinates, 
306 

non-Isometric   lines,   305 

Joints,  232,  233 

Lead,   258 
Lettering 

form  and  proportion  of,  22 

inclined,  lower  case,  slope  of,  192 

in  ink,  25,  102 

in  pencil,  24 

pencil,  28 

plate,   28 

position  of  hand  in,  24 

preparation  of  tracing  cloth,  102 

slope,  194 

spacing   of,    23 

strokes  for,  23 
Levels 

scale  of,  cylindrical  objects,  45 

scale  of,  rectangular  objects,  31 
Line 

border,  172 

dotted,  76 

invisible,   76 

notation,  171 

object,   172 

table,  35    ' 

Linear  distance,  measuring,  268 
Line,  center 

circular,   100 

principal,   100 

radical,  100 

secondary,  100 
Lines 

Crosshatch,  172       » 

extension  and  dimension,  136 

in  perspective,  direction  of,  11 

Isometric,  305 

non-Isometric,  305 

object,  171 

Parallel  lines,  125 
Perpendicular  lines.  125 


INDEX 


331 


Machine  drawing,  247 
Machine  screws,  258 
Marks,  foot  and  inch,  30 
Material,  bill  of,  247 
Measure 

cube,   definition,   34 

cube  in  new  positions,  57 

cylinder,  horizontal,  52 

cylinder  in  new  positions,  58 

cylinder,   vertical,   44 
Measurements 

accuracy  of,   267 

center-to-center  of  holes,  272 

in  foreshortening,  13 

in  perspective,  31 

iinear  distances,  268 

radii,  273 

taking  of,  267 
Measuring  instruments,    265 
Multiple  thread,  258 

Notation  of  lines,  171 
Notes,  137 

Number  and  fraction,  43 
Nuts  and  bolts,  255 

Object 

lines,   172 

sketching  from,  261 
Orthographic 

front  and  side,  81 

review,   orthographic   sketching,   104 

sketching,  66 

top  of  front,   67 

views,  definition,  66 
Outside  diameter,  measuring  of,  270 

Paper 

blueprint,  166 

coordinate,   263 

drawing,  15,  119 

to  fasten  to  the  board,  15 

tracing,   166 
Partial  yiew,  228 
Pen 

bow,  171 

care  of,  169 

filling,  167 

ruling,  167 
Pencil 

drawing,  16 

lettering,  28 

review   questions,   pencil   mechanical 
drawing,  154 

to  sharpen,  17 
Pencils 

manipulation,   126 

requisites  of,  125 


Perspective 

concentric   circles  in,  48 

direction  of  lines  in,  11 

horizontal   measurements  in,   34 

measure  cube  in  new  positions,  57 

measure  cylinder  in  new  positions,  58 

measurements  in,  31 

review  questions,  perspective  sketch- 
ing, 61 

sketch,  definition  of,  10 

the  cube  in,  13 

the  measure  cube  in,  34 

the  table  line,  35 

to  center  sketch  on  sheet,  40 
Perspective  -sketching 

constructive  stage  in,  18 

enclosing  solid  in,  34 

finishing  stage  in,  18 

materials   for,   15 
Pipe  threads,  255 
Pitch 

of  thread,  249 

Plane  surfaces,   representation  of,   68 
Problems 

three  view,   110 
Proportional  inch  scale,  128 

Quarter  section,  99 

Radii,  measuring,  273 
Radius  dimensions,  150 
Rectangle 

border,  133 

enclosing,   133 
Rule,  folding,   265 
Ruling  horizontal  lines,  126 
Ruling  pen 

adjustment  of,  167 

care  of,   169 

filling,  108 

manipulation  of,  168 

requisites  of,  167 

sharpening,  169 
Ruling  vertical  lines,  126 

Scale 

of  levels,   cylindrical,  45 

of  levels,  rectangular,  31 

steel,  265 
Scales 

architect's,   127 

engineer's,  127 

proportional  inch,   128 
Screw 

cap,  258 

machine,  258 

set,  258 

wood  screws,  231 


332 


INDEX 


Screw  threads 

acme,  253 

pipe,  255 

square,  253 

TJ.  S.  Standard,  252 

V-Thread,  250 
Sectional  views,  227 

breaks,  229 

broken  line,  228 

half  section,   98 

partial,  228 

quarter  section,  99 

revolved  section,  228 

section    through    ribs,    shafts,    bolts, 
228 

separate  section,  229 
Section  lining,   171 
Set  screws,  258 
Sharpening  pencil,  17 
Shield,   erasing,   132 
Sketch,  perspective 

constructive  stage,  18 

finishing  stage,  18 

perspective,   definition   of,   10 

to  center  on  sheet,  40 
Sketching 

a  circle,  101 

from  the  object,  261 

orthographic,   66 
Springs,    255 
Square 

adjustable,  266 

T-,  119 

threads,  253 
Straight  edges,  69 
Strokes 

curved,  37 

horizontal  in  lettering,  55 

inclined  in  lettering,   189 

vertical  in  lettering,  55 
Strokes 

in  lettering,  23 

in  lettering,   order,   number,  and  di- 
rection of,  23,  28 
Stud,  258 
Stud  bolt.  258 
Sub-title,  279 
Surfaces 

cylindrical,  representation  of,  92 

cylinder  and  cone,  223 

development  of  a  surface,  definition 
of,  189 

inclined,  81 


intersection  of  surfaces,  213 
plane,  representation   of,   68 
prism  and  cylinder,  217 
two  cylinders,  220 

Table  line,  35 
Tacks,   thumb,    16 
Tangencies 

construction  of,   325 

locating  points  of,  184 
Tap  bolt,  258 
Thread 

multiple,  258 

pipe,  255 

screw,  249     (See  Screw  Threads) 
Three  view  problems,  110 
Thumb  tacks,   16 
Title,  block,  138 
Title,  sub,  279 
Titles 

balance,  27,  140 

commercial,    139 

contents  of,  139 

design  of,  26 

steps  in  design,  26 

trial,  sheet,   140 
Tracing 

cloth,   161,   165 

paper,  166 

tracing  and  blueprinting,  185 

trimming  the,  173 
Triangles 

use  of,  121 

combination  of,  124 

direction  of  drawing  lines,  124 

testing,  122 

30°  to  60°,  122 

45°,  122 

T-square,  119 

U.  S.  Standard  thread,  252 

Vanishing  points,   definition   of,   11 
Vertical  lines,  ruling,   126 
Views 

arrangement  on  sheet,  140 

definition  of,  66 

partial,  228 

relation  of  front  and  side,  81 

relation  of  top  and  front,  67 

sectional,  227 


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